udio & hi-fi computers ... - world radio history

UDIO & HI-FI COMPUTERS & MICROPROCESSORS DESIGN IDEAS RADIO, TELEVISION & COMMUNICATIONS SCIENCE & TECHNOLOGY TEST & MEASUREMENT

Please mention ELEKTOR ELECTRONICS when contacting advertisers

ROM CONCEPT TO ARTWORK IN 1 D

ULTlboard/ULTIcap evaluation system: all features of the bigger versions full set of manuals design capacity 500 pins s 95Price incl. S & H, excl. VAT:

Purchase price is 100% credited when upgrading toa bigger version. Also suitable for study & hob

Your design ideas are quickly captured using the ULTIcap schematic design Tool. ULTIcap usesREAL TIME checks to prevent logic errors. Schematic editing is painless; simply click your start and enpoints and ULTIcap automatically wires them for you. ULTIcap's auto snap to pin and auto junctionfeatures ensure your netlist is complete, thereby relieving you of tedious netlist checking.

ULTIshell, the integrated user interface, makes sure allyour design information is transferred correctly fromULTIcap to ULTlboard. Good manual placement tools arevital to the progress of your design, therefore ULTlboardgives you a powerful suite of REAL-TIME functions suchas. FORCE VECTORS. RATS NEST RECONNECT andDENSITY HISTOGRAMS. Pin and gate swapping allowsyou to further optimise your layout.

CallE1 LEM 12E133

. 1 . 1 . 1 1 . 1_

Nov; you can quickly route your critical trULTlboard's REAL-TIME DESIGN RULE CHECKwill not allow you to make illegal connections orviolate your design rules. ULTlboard's powerfulTRACE SHOVE, and REROUTE -WHILE -MOVEalgorithms guarantee that any manual trackediting is flawless. Blind and buried vias andsurface mount designs are fully supported.

If you need partial ground planes, thenwith the Dos extended board systems youcan automatically create copper polygonssimply by drawing the outline. The polygonis then filled with copper of the desired net,all correct pins are connected to thepolygon with thermal relief connectionsand user defined gaps are respectedaround all other pads and tracks.

ULTlboard's autorouter allows you tocontrol which parts of your board areautorouted, either selected nets, or acomponent, or a window of the board, orthe whole board. ULTlboard's intelligentrouter uses copper sharing techniques tominimise route lengths. Automatic viaminimisation reduces the number of vias todecrease production costs. The autorouterwill handle up to 32 layers, as well assingle sided routing.

ULT1board's backannotation automaticallyupdates your ULTIcap schematic with any pinand gate swaps or component renumbering.

aFinally, your design is post processed to generatepen / photo plots, dot matrix/laser or postscriptprints and custom drill files.

ULTlboard PCB DesigniULTIcap

Schematic Design Systems are available

in low-cost DOS versions, fully compatible

with and upgradable to the 16 and 32 bit

DOS -extended and UNIX versions,

featuring unlimited design capacity.

4E edgem.0.4ze

ULTImate Technology UK Ltd. 2 Bacchus House, Calleva Park, Aldermaston Berkshire RG7 40W Fax: 0734 - 815323 Phone: 0734 - 812030

January 1995ELEKTUR Volume 21CONTENTS Number 229ELECTRONICS ISSN 0268/4519

In next month's issue

FOCUS ON: Computer-aided design (CAD) ofprinted -circuit boards and

circuit diagramsDolby surround processorMIDI multiplexerMOSFET inverterThe op amp revisitedParameters of RF amplifiers

and others for yourcontinued interest.

Front coverThe photograph shows adigital -to -analogue converterwhich is intended to beconnected directly to acompact disc player ordigital cassette recorder. Aspecial feature of the unit isthe possibility of feeding itsclock signal to the digitalsound source to prevent theconversion causing any jitter.Including the power supply,it is contained on a printed-circuit board rather smallerthan eurocard size.

Copyright © 1995 Elektuur BV

. # s

36 Selecting voltage referencesMaxim Application

I

8 Dolby Surround: What is it? How does it work?Based on an article by D. Laues

14 PROJECT: Mini audio digital -to -analogue converterDesign by T. Giesberts

a al'

28 Self -loading EEPROM Type X88C64By our editorial and design staff

0 ,1 .., I z.. I # ;22 PROJECT: Debugging 8031/8051 microcontroller

systemsBy Dr M. Ohsmann

58 FOCUS ON: Debugging PCsBy M. Rathjen

0.

5 Communications in EuroTunnel's hostile sub -seaenvironmentBy Bill Pressdee

44 The Digital Solution - Part 2By Owen Bishop

52 PROJECT: Quasi -analogue clockworkDesign by P. Hogenkamp

74 PROJECT: 1 -to -3 -phase converter - final partDesign by B. Yahya

I II I 4

73 PROJECT: In -line A/V tester for LNCsDesign by G. Kleine

i ° a I * '1

81 Book availability & prices82 Buyers' guide34 Corrections & Updates82 Index of advertisers78 Readers' services81 Switchboard80 Terms of Business

Communicationshostile

,// --

'n

C7a .11

in EuroTunnel'ssub -sea environment - p. 5

, -10

...,

DolbyHow

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1

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surround. What isdoes it work? - p.

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Debugging 8031/8051 micro -controller systems - p. 22

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ABCAUDIT BUREAU OF CIRCULATIONS

Self -loading EEPROMType X88C64 - p. 28CONSUMER PRESS

Elektor Electronics is published monthly, except in August, by Elektor Electronics (Publishing), P.O. Box 1414, Dorchester, Dorset DT2 8YH, England. The magazine isavailable from newsagents, bookshops, and electronics retail outlets, or on subscription at an annual (1994/95) post paid price of £28.00 in the United Kingdom; air speeded:

£3500 in Europe, £44.00 in Africa, the Middle East and South America; £4600 in Australia, New Zealand and the Far East; and SUS 59.00 in the USA and Canada. Second

Class Postage paid at Rahway N.J. Postmaster: please send address corrections to Elektor Electronics, c/o Mercury Airfreight International Inc., 2323 Randolph Avenue,

Avenel, New Jersey, N.J. 07001.

ELEKTOR ELECTRONICS JANUARY 1995

4 Please mention ELEKTOR ELECTRONICS when contacting advertisers

ESR ELECTRONIC COMPONENTSStation. Road, Cullercoats,Tyne & Wear NE30 4PQTel. 091 251 4363 Fax. 091 252 2296

DEPT. EE

74LS- Ser ies

74LS0074LS0174LS0274LSO3741.90474LS0574LS0874LS0974LS1074LS1077415109741_51174LS11274LS11374LS11474LS1274LS12274LS12374LS12574LS12674LS1374LS13274LS13374L013674LS13874LS13974LS1474LS14574LS14774LS141374LS157415151741515374151547415155741515674151577415158741516074151617415162741516374151647415165741517074151737415174741_51757415190741_5191741519274151937415195741519674151977415207415217415227415221741524074L024174LS24274LS24374LS24474LS24574LS24774LS25174LS25774LS25874LS2674LS26674LS2774L027374L027974LS3074LS3274LS36574LS36774LS36874LS3774LS37374LS37474L037574LS37774LS37874L53874LS39074LS39374LS39574LS39974LS4074154274LS4774L55174LS67074LS7374LS7474L57574LS7674LS8374L98574158674L99074LS9274LS93

£0.22£0.14£0.14£0.14£0.14£0.14£0.14£0.14£0.14£0.23£0.21£0.17£0.21£0.21£0.21£0.14£0.31£0.31£0.21f0.21£0.14£0.21£0.18£0.16£0.24£0.25£0.18£0.56£1.26£0.70£0.14£0.25£0.25£0.70£0.25£0.36£0.25£0.25£0.32£0.32£0.32£0.32£0.26£0.48£0.30£0.24£0.24£0.24£0.25£0.24£0.42£0.24£0.24£0.24£0.24£0.16£0.14£0.14£0.36£0.32£0.32£0.32£0.32£0.32£0.36£0.32£0.24£0.24£0.24£0.14£0.14£0.14£0.32£0.25£0.14£0.14£0.21£0.21£0.21£0.14£0.32£0.32£0.34£0.32£0.62£0.14£0.25£0.24£0.26£0.62£0.14£0.25.,2.13 72

£0.14£0.69£0.17EC 26£0.19£0.25£0.31£0.35£0.20£0.23£0.35£0.26

ENAMELLEDCOPPER

WIRE

All 2oz Reels14 SWG 806316 SWG £0.6718 SWG £0.6720 SWG £0.7222 SWG £0.7624 SING £0.8026 SWG £0.8928 SWG £0.9130 SWG f0,9332 SWG £0.9334 SWG £0.9936 SWG £1.0438 SWG £1.1040 SWG £1.22

4000 Series

400040014002400640074008400940104011401240134014401540164017401840194020402140224023402440254026402740284029403040314033403440354040404140424043404440464047404840494050405140524053405440554060406340664013740684069407040714072407340754076407740814082408540864089409340944095409740984099450245034508451045114512451445154516451845204521452645274528452945324534453645384541454345554556456045664572458445854724401064010940163401744017540193

£0.17£0.21£0.17£0.40£0.28£0.31£0.19£0.23£0.26£0.16£0.21£0.30£0.31£0.1840.27£0.27£0.19£0.31£0.31£0.32£0.16£0.21£0.1540.59£0.18£0.22£0.360.17£0,70£0.56£1.24£0.31£0.29£0.31£0.22£0.2840.35£0.3140.48£0.31£0.20£0.20£0.36£0.25£0.25£0.5640.34CO 48£0.29£0.18£1.91£0.16£0.20£0.17£0.20£0.17£0.17£0.17£0.30£0.17£0.14£0.21£0.28£0.26£0.55£0.30£0.31£0.56£1.20E0 48£0.38£0.38£0.31£0.90£0.26£0.3240.32C0.7740.98£0.31£0.27£0.26£0.62£0.40£0.40£0.40£0.44£0.32£2.48£1.00£0.3740.33£0.46£0.34£0.34£1.18ft .96£0.25£0.24£0.32£0.70£0.31£0.50£0.46£0.34£0.36£0.60

-2911613 £0.31 BC186 £0.33 BD534 £0.472911711 £0.26 BC204C £0.72 BD535 £0.482911893 03.29 BC206E1 £0.72 60535 £0.6529122184 £0,28 BC207C £0.72 BD646 £0.522N2219A £0.25 BC208 £0.72 50648 £0.522N2222A f0,16 802094 £0.72 BD650 £0.532912646 £0.80 BC212 £0.08 130707 £0.422N29044 £0.25 BC212L £0.08 80807 £0.802N29054 £0.23 BC212LB £0.08 BDX32 £1.782912907 £0.20 BC213 £0.08 BDX33C £0.462912926 £0.16 BC213LC £0.08 1308340 £0.502913053 £0.27 BC21 4 £008 8DX53C £0.472913054 £0.90 BC214L £0.08 BOX54C £0.502N3055 £0.62 BC23713 £0.09 8E180 £0.312913440 £0.50 BC238C £0.09 (3E182 £0.312913702 £0.09 602390 £0.10 B F185 £0.312913703 £0.10 BC251 £0.13 13 F194 £0.192143704 £0.10 BC252 £0.13 BF195 £0.192913705 £0.10 BC2616 £0.24 8F244 £0.352913706 0.10 BC2628 £0.24 BF257 £0.332913771 £1.44 BC2678 £0.30 BF259 £0.332913772 £1.51 8 0307 £0.10 F337 £0.362913773 £1.79 80308 £0.10 BF355 £0.382913819 £0.40 BC327 £0.10 8F423 £0.132913820 £0.58 80328 £0.10 BF451 £0.192913904 £0.10 BC337 £0.10 8£459 £0.332913905 £0.10 80338 £0.10 BF469 £0.362913906 £0.10 604140 £0.13 BFX29 £0.292914036 CD 31 BC441 £0.40 BFX84 £0.312915296 CD 57 13C461 £0.40 BFX85 £0.312915321 £0.57 BC463 £0.29 BEY50 £0.292916107 £0.60 BC478 £0.32 8E951 £0.26AC126 £0.30 BC479 £0.32 BEY52 £0.28AC127 £0.30 BC490 £0.24 BS107 £0.21AC128 £0.28 BC516 £0.22 89170 0.21AC187 40.45 BC517 £0.20 RSW66 £1.35AC188 £0.37 80527 £0.20 BU126 £1.70ACY17 £3.84 BC528 £0.20 BU205 £1.8240149 £1.67 80537 £0.20 8U2084 £1.73AD161 £0.92 BC546C £0.08 8U3264 £1.80AD162 £0.92 BC547C £0.09 8U500 £2.32BC107 £0.14 BC548C £0.08 8U5084 £1.76BC1078 £0.15 BC549C £0.10 BU526 £2.24BCI 08 40.14 8C550C £0.08 8U806 £1.36BC1084 £0.14 BC556,4 £0.08 BUX84 £0.78BC108C £016 80557C £0.08 IRF540 £1.60BC1098C109C

£0.14£0.17

BC558C8C559C

£0.08£0.08

IRF740MJ11015

L1.80£2.11

BC114 £0.41 805608 £0.09 MJ11016 £2.11BC115 £0.41 80637 £0.21 MJ2501 £1.60BC116 £0.41 80638 £0.21 MJ3001 £1.52BC118 £0.41 80639 £0.21 MJE340 40.40BC132 £0.36 50640 £0.21 MJE350 £0.42BC134 £0.36 BCY70 £0.21 MPS413 £0.12BC135 £0.36 BCY71 £0.20 MPSA42 £0.17BC140 £0.25 BCY72 £0.20 MRF475 £6.21BC141 £0.27 BD135 £0.20 TIP121 £0.35BC142 £0.31 80136 40.21 TIP122 40.40BC143 £0.34 80137 £0.22 TIP125 £0.37BC149 £0.21 BC/138 £0.22 TIP127 £0.37BC154 £0.36 80139 £0.23 TIP132 £0.46BC157 £0.12 8 D140 £0.24 TIP137 £0.46BC159 £0.12 BD150C £0,82 TIP142 £1.0813C150 £0.28 00165 £0.42 TI P147 £1.12BC170 £0.16 E33166 £0.35 TIP2955 £0.63BC170/3 £0.16 83187 £0.39 TIP29C £0.31BC171 £0.11 BD201 £0.40 TIP3055 £0.63BC1718 £0.16 80202 £0.40 TI P300 £0.3180172 £0.13 B D203 £0.40 TIP31C £0.34601726 £0.13 EI 0204 £0.40 TIP32C £0.32BC177 00.18 8 D222 £0.40 TIP33C £0.72BC178 10.18 8 0225 £0.42 TIP4IA 00.4880179 £0.17 8 D232 £0.38 TIP42C £0,38BC182 £0.08 B D237 £0.32 TI P47 £0.48BC1821 £0.08 E3 0238 £0.32 TI P48 £0.62BC18218 £0.08 0240/3 £0.37 TI P50 £0.53BC183 £0,08 130243B £0.50 VN1OKM £0.44BC183L £0.08 BD2444 £0.53 VN66AF £1.50BC183LB £0.08 133246 £1.06 ZTX300 £0.16BC184 £0.08 813441 £0.41 ZTX500 £0.16BC184L £0.08 80442 £0.41

TRIACS

7102060 agLTM00BTIC23611) £0.96DIAC £0.20

VOLTAGEREGULATORS

78L0578L1 2781157910579112791157805781278157905791279151M317TLM723L200CVLM323KLM338K

£0.24£0.24f0.24£0.28f0.28£0.28£0.28£0.28£0.28£0.38£0.38£0.38£0.65£0.29£1.16£2.70£5.52

OPTO DEVICES5mm Red LED5mm Green LED5mm Yellow LED5mm Orange LED3mm Red LED3mm Green LED3mm Yellow LED3mm Orange LED5mm Flashing Red5mm Flashing Green5mm 0 Colour5mm Tn Colour5mm Plastic Bezel3mm Plastic Bezelo.r 7 Segment Display Redcommon anodecommon cathode

A

£0.09£0.10£0.10£0.10£0.08£0.12£0.13£0.13£0.50£0.54£0.36£0.48£0.04£0.05

£1.14£1.14

THYRISTORSPO10244TIC10607101160TIC126D

£0.30£0.40£0.66£0.77

HARDWARET2 Box 75 x 56 x 25mm £0.8273 Box 75 x 51 x 25mm £0.8214 Box 111 x 57 x 22mm £0.98M81 Box 79 x 61 x 40mm £1.44M82 Box 100 x 76 x 41mrn £1.56MB3 Box 118 x 98 x 45mm £1.82M85 Box 150 x 100 x 60mna £2.50

LINEAR ICs

CA311ECA324CA555CA741 CECA74706CA3046CA3080CA3130CA3130ECA3140CA3240ICL7621ICM7555ICM7556LM3014LM348NLF351 NLF353LF356LM358NLM377LM380NLM381LM386LM387LM392NLM393NLIVI748CNLM1458L M39001M3914LM3915MC3340MC4558NE531NE556INNE567NNE5532NE5534TBA1205TBA810STBA820MT042030TL061TL062TL0641.071CPTL072CPTL074CNTL081TL082CP1.084CN04733ULN 2003ULN2004ZN414ZZN425EZN426EZN427EZN428EZN435EZN448E

£0.28£0.26f0:22'80.28£0.39£0.37£0.72£0.98£0.96£0.56C1.12

£1.70£0.43£0.96£0.25£0.31£0.36£0.41L0.84

£0.27£2.57£1.12£2.70£0.48£1.60£0.79£0.28£0.31£0.26£0.72£2.70£2.70£1.60£0.36£1.56£0.36£0.36£0.80£0.66£0.77£0.68£0.39£1 .35£0.35£0.42£0.46£0.32£0.34£0.48£0.33£0.34£0.46£0.64£0.52£0.48£1,04£4.68£2.61£8.82£6.12£5.31£7.92

EPROMS &RAMS

271627322764-2527064-2521728-20270128.2027256-2027C255-20

2705122700106116-106264-1062256.104164-1541256.10511000.8514256-8

44.4644.84£3.0042.8043.6943.31C3.99£3.57

43.6944.9741.53£3.0644.8341.78£2.8045.6145.61

DIL SOCKETS8 Pin14 Pin10 Pin18 Pm20 Pin24 Pin28 Pin40 Pin

£0.07£0.11£0.15f0.15£0.16£0.19£0.22£0,25

ELECTROLYTIC RADIAL CAPACITORS

uF0 471.02.247102247100220470100022004700

16V

£0.05£0.05£0.06£0.06£0.09£0.15£0.22£0.37

25V

£0.05£0,05£0.06£0.09£0.12£0.19£0.29£0.57£1.11

63V£0.05£0.05£0.05£0.05£0.06£0.09£0.11£0,11£0.31£0.57

£0.07£0,06£0.06£0.08£0.08

100V 450V

£0.15£0,18£0.30£0.48

ELECTROLYTIC AXIAL CAPACITORS

11 -

Ante( Soldering irons BNC Solder Plug 506

S.

£0.93M 12 Wan 03.50 BNC Solder Plug 75R E0.96C 15 Wad 48.19 BNC Crunp Plug 50R £0.68G IS Watt £8.75 BNC Crung Plug 75R £0.68CS 17 Watt £8.65 BNC Solder Skt £1.08XS 25 Watt. £8-75 BNC Chassis Skt £0.80GA5CAT 15.87 P12595 2rnm £0.68ST4 STAND f2.85 PL259 lImm £0.6235 Wall Gas Iron £11.58 RND UHF socket £0.68Desolder Pump £3.00 509 UHF socket £0.45Antistatic Pump £4.30 F Plug RG58 £0.3022SWG 0,5Kg Solder £7.40 F Plug RG6 £0.2718SWG 0,5Kg Solder £6.60 N Plug RG8 £1.60lmm 3 yds Solder £0.62 N Socket RG8 £1.40Desolder Braid £0.87 BNC Crimp Pliers £15.50

PCB EQUIPMENTUV EXPOSURE UNIT £67.38PLASTIC DEVELOPING TRAY £1 .35PHOTO RESIST AEROSOL SPRAY (100m1) £3.90FERRIC CHLORIDE CRYSTALS (0 5Kg) £2.45TIN PLATING POWDER (90g) £10.80ETCH RESIST PEN £0.72PCB POLISHING BLOCK £1.84

STRIPBOARD 01 PITCH BREADBOARD64mm x 25mm £0.27 81mm x 60mm £3.0664mm x 95mm £0.90 175mrn x 42rnrn £3.7464mm x 431 mm £3.22 175rnm x 67rnm £5.5695mm x 127mm £1.50 203rnm x 75mm includes95mm x 95mm £1.10 mounting plate & posts £7.3695mm x 431mm E4.80 COPPER BOARD (G. Fibre)100rnm x 160narn £1.60 100mrn x 160mm £0.90119mm x 454rnm £6.20 110mm L 220mm £1.24

PHOTO RESIST BOARD PHOTO RESIST BOARD(G. Fibre) (Paper)

£0,86£1.62£2.09£2.41

CAPACITORSCeramic Mini Disc 100 & 638

1 OpF to 100nF1 pF-1nF £0.06 1n2 -2n7 £0.073n3.4n7 £ 0.1210n & 12n £0.07

Polystyrene 160V 5% 47pF to 10nE47p -2n2 £0.09. 2n7 -10n £0,12

D CONNECTORSPlug Socket

9 Pm £0.29 £0.3015 Pin £0.39 £0.3915 Pin H D. £0.81 £0.9023 Pin £0.40 £0.4925 Pia £0.48 £0.50

9 Way plastic cover £0.3015 Way plastic cover £0.3323 Way plastic cover £0.3625 Way plastic cover £0.36

BRIDGERECTIFIERS

W0051 54 50VW021 5A 200VBR32 3A 200VBR62 6A 200V100410A 400V

£0.19£0.20£0.3640,70£1 39

8 x 10"

£0.67ft .24f1.58£4.63

SWITCHES3amp 250v 6 4rom /3 mountingSPST Toggle £0.58SPOT Toggle £0.60SPDT CO Tog £0.64DPDT Toggle £0.68DPDT CO Toggle £0.76DPDT CO Toggle(biased) £1.20DPDT CO Toggle(biased 1 way) £1.20DPDT men slide £0.15Rotary Wafer 1 P -12W. 2P-6VV,3P -4W, 4P -3W £0.78Key Sworn SPST £2.70Push to make £0.25Push to break £0.28Latching Push Sur £0.63PCB Tact 6 x 6mm £0.25

RESISTORS0 25W 5% CF El 2 Series £0.60/10005W 5% CF E12 Series £0,95/1,00025W 1% MF E24 Series £1 .72/100POTS Log or Lin 470R IMO 25mm die 0.25w

£0.425 aftPRESETS Enclosed Hort

or Vert 1006 IMO 0.15WPRESETS Skeleton Hera

or Vert 100R IMO 0 1W £0.11

£0.15

* PLEASE STATE VALUE REQUIRED *

DIODESCOMPUTER ACCESSORIES

Parallel Printer Lead 2mRS232 Lead (all pins) Male Male

£6.90E3.75

Zener Diodes 2V7 33VBZY88400Mw £0.08

RS232 Lead (all pros) Female Male C3,80 88085 1 3W £0.14Centronics 36 Way Lead Male Male £4.78 1 N4001 £0.06Gender Changers 1 N4002 £0.079 Way D Mini Female to Female 01.81 1 N4003 £0.079 Way D Mini Male to Male £1.98 1 N4004 £0.0725 Way D Mini Female to Female £2.23 1 N4005 £0.0725 Way D Mini Male to Male9 Way D Female to Female9 Way D Male to Male

£2.23£2.33£2.33

19140061 N4007

£0.08£0.08

25 Way D Female to Female £2.71 1N5400 £0.0925 Way D Male to Male £2.71 1 N5401 £0.09Adaptors 1915402 £0.099 Way Mate to 25 Way Female £2,71 1915404 £0.119Way Female to 25Way Male £2.71 1 N5406 £0.1125 Way Male to 9 Way Female C2.33 1 N5407 £0.1425 Way D Male to 36 Way Centro= £3.56 1 N5408 £0,1525 Way Null Modem Female Female £3.02 1 N914 £0.0625 Way Null Modem Male to Female25 Way Null Modem Male to MaleRS232 Sorge Protector Male Female

£3.02£3.02£6.12

1 N9161 N4148

£0.06£0.05

RS232 Jumper Box Male to Female £3.02 89133 £0.13RS232 Tester (7 LEDs) Male Female £6.59 0A47 £0.28Data Switch Boxes OA90 £0.07Serial Switch box 2 Way A/B £9.20 0491 £0.10Serial Smirch box 3 Way AiENC £13.16 0A202 00.29Serial Switch box 4 Way 4/8/C/D £15,15 BA157 £0.10Senal Switch box Cross overParallel box . 2 Way A/B

£19.69£11.84 BA158 £0.10

Parallel box 3 Way A/B/C/ £17.11 BA159 £0.10Parallel box . 4 Way ArRfC/0 £18.43 1 N4149 £0.06Parallel box Cross over £20.42 0A200 £0.10

ORDERING INFORMATIONuF 16V 25V 63V 10011 450V All prices exclude VAT.0 47 £0.15 Please add £1.25 carriage to all orders and VAT (17.5%)1.02.2

£0.10£0.10

£0.10£0.10

£0.19£0.22 No minimum order charge.

44)7 £0.09£0.12

£0.10£0.12

£0.10£0.12

£0.34£0.48 Free Computer listing with all orders over £5.00.

2247 £0.10

£0.09£0.11

£0.13£0,16

£0.17£0.20

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COMMUNICATIONS IN EUROTUNNEL'SHOSTILE SUB -SEA ENVIRONMENT

'tog..1P-114.

' li

FuroTunnel, running 91 m below the waves of the EnglishChannel, is the seabed umbilical which has finally recon-

nected Britain to Europe after a severance of many thousandsof years.

There are three tunnels, each 25 km long, linking Cheritonnear Folkestone in the UK and Coquelles, near Calais, in France.Two running tunnels are for trains, and a service tunnel formaintenance staff and maintenance vehicles, which can alsoprovide an emergency evacuation route.

The two terminals have large rail loops with loading and un-loading platforms. Shuttle trains which are 750 m long operateat 140 km/h through the tunnel and circulate the loops at theterminals, providing a continuous service for transport of cars,coaches and lorries.

Tourist wagonsThe shuttle trains are made up of rolling stock which comprisesHGV (heavy goods vehicles) wagons, and double or single -deckTourist Wagons. International freight and passenger trains be-tween London and continental destinations traverse the tunnelat 160 km/h.

The complexity of operating a major utility of this magnitudehas made heavy demands on the design of the communicationsequipment required for the enterprise. In December 1989, theAnglo-French construction company, Trans -Manche -Link (TML),awarded the channel tunnel communications contract to MotorolaLand Mobile Products Sector (LMPS), based at Basingstoke insouthern England.

Dedicated teamThe considerable scope of the TML communications require-ment to be met by Motorola necessitated the setting up of a ded-icated channel tunnel team at Camberley near Basingstoke,which was supplemented by a hardware and software designgroup located at Copenhagen in Denmark. The combined teamshave been working closely with TML to design, develop, manu-facture and maintain systems designed to operate for 20 years.

Five integral radio systems are involved; this article is con-cerned primarily with the concession radio system and the shut-tle internal radio system, both of which were designed at Camberley.

The five systems comprise:1. Concession radio.

Designed at Camberley and manufactured at LMPS head-

quarters, this system provides general communications forterminals in the UK and France and both running and ser-vice tunnels.

2. Track -to -train radio.Designed in Denmark and manufactured at Basingstoke,these radios provide communications between the shuttletrain driver and control centres in the UK and France.

3. Paging.Manufactured by the Motorola Paging and Wireless DataGroup in Boynton Beach, Florida, the paging system pro-vides communications for management and maintenancepersonnel in UK terminal areas.

4. Shuttle internal radio.Designed at Camberley and manufactured at Basingstoke,this system provides a VHF link to car FM radios and on-board driver to captain.

5. Radiating cable (leaky feeder).This comprises 300 km of tuned UHF cable, of French manu-facture, installed in the running and service tunnels andshuttle vehicle. It acts as an antenna for the transmissionand reception of radio signals from track to train and con-cession trunked system, while another application is for theshuttle internal radio.

Design guidelinesSystem reliability and security were prerequisites in the designparameters adopted. Redundancy in design and architecturewas an overarching requirement with duplication of all majoritems of control equipment, in such a way that radio access isavailable at any site if a failure occurs. To this end, the track -to -train system uses a hot standby configuration with one con-troller in the UK and the other in France. The Concession Systemdesign arranges that each radio base station is connected to twoseparate trunk controllers.

The transmission system bearer network interface has beenarranged to support this philosophy and architecture as evi-dent in the alternate connection of 'odd' and 'even' base stationsand the use of alternating base transmission frequencies on theConcession System.

A number of issues arose owing to the complexity of frequencyplanning and different usage by the UK and France of the UHFband as well as blocking and intermodulation problems causedby close proximity of equipment in the tunnel environment.These were resolved after prolonged discussion of the plan.

Tough specificationAll equipment designed for use in the EuroTunnel has to meetsevere environmental criteria. These are much akin to those navalequipment must sustain in tropical usage and imply a marineclimate with high humidity and a saline atmosphere. Temperaturesmay approach 35 °C with high humidity in the equipment roomstowards the centre section of the tunnel system.

In consequence, equipment racks have been fabricated from2.5 mm marine -grade stainless steel, while all radio and ancil-lary equipment is fully sealed against ingress of dust and metal-lic particles, particularly from brake shoes, the necessity foradequate ventilation of units having been taken fully into con-sideration.

The vibration requirements apply not just to on -board equip-ment but also to trackside equipment which will be affected bythe continual passage of trains at up to 160 km/h. Protectionis needed to counter the very high electromagnetic field createdby the shuttle locomotives, which is in excess of the normal op-erating RF/EMC (electromagnetic compatibility) environmentof radio equipment and is similar to that specified for military


6 COMMUNICATIONS IN AND AROUND THE EUROTUNNEL

equipment.Particular attention has been paid to earth bonding of equip-

ment and the introduction of EMC/RFI (radio frequency inter-ference) filters in all control lines to radio base station. All majoritems of control and radio equipment have therefore been testedagainst IEC (International Electrotechnical Commission) spec-ifications and ETSI (European Telecommunications StandardsInstitute) Res 9 guidelines.

Fire hazardThe considerable experience gained from operation of LondonUnderground has brought to the project an awareness of thedangers of fire hazard in underground systems. Therefore, ahigh degree of fire retardency and halogen -free materials havebeen specified for all exposed equipment and cabling.

The Concession Radio System, which is based on a conven-tional multi -site, multi -channel MPT1 327 trunked radio sys-tem, provides general communications in all three tunnels foroperations and maintenance staff and to despatchers in the UKand France rail control centres.

The staff are equipped with hand portable transceivers andprovide a back-up system for the EuroTunnel train drivers; theyare also fitted in the shuttle terminal transport vehicles that op-erate in the service tunnel.

Control channelsTherew are two separate control channels available at each basestation. Each supports a number of traffic channels providingboth speech and data communication between operations andmaintenance hand portables, and to the control centres, andspeech between mobiles and portables and the PABX (privateautomatic branch exchange) network and also outbound PSTN(public switched telephone network) connections.

The types of speech call supported are: individual speechcalls, group speech calls, group broadcast calls, despatchercalls, PABX calls and outbound PSTN calls. The data calls sup-ported are: status calls, despatcher data calls and mobile textmessages.

The architecture of the Concession System divides it intothree areas: the UK Terminal (one base site); the Tunnel Zone,incorporating all three tunnels; and the French Terminal (threebase sites).

There are 35 radio base station sites each serving all threetunnels. Each radio base station comprises two sections, eachcontrolled via the bearer network from separate trunk controllersto provide redundancy. In the terminal areas, the base stationsuse conventional antennas, whereas in each of the three tun-nels each base station is connected to the leaky feeder.

A tunnel site serves a 1500 m tunnel section and is linkedseparately, via bearer circuits, to trunk controllers in both theFrench and UK terminals. Odd -number tunnel sites are con-nected in parallel before presentation to the respective trunkcontrollers, as are the even -number tunnel sites.

Internal radioThe Shuttle Internal Radio System is a hand portable to handportable radio system for use within the EuroTunnel touristwagons. It can also be accessed from the Train Captain's ControlPanel position in each locomotive cab.

The system can be used to provide public address and in-tercommunications and to act as an emergency telephone. Leakyfeeder cable is fitted throughout the train connected by PCM(plug compatible manufacture) links in each wagon and termi-nated at each end of the train by a repeater base station fittedin the locomotive. This enables the crew to use their hand portablewhen moving throughout the train.

The portables transmit on a common base receive frequencyon one of 20 available CTCSS (continuous tone control squelchsystem) channels and each end repeater votes its locally receivedsignal against the remote received signal, routed via the through -train PCM link. Each end repeater transmits on one of two basetransmit frequencies, and the portables scan on each of the 20channels between these two frequencies. This is necessary toprovide coverage over the length of a full rake (a line of wagonscoupled together as one unit) train as the losses in wagon cou-plers preclude coverage from one end of the train only.

Tourist trains are provided with a VHF FM (88-109 MHz)transmitter and tape system to provide two channels of prere-corded audio, one in English, the other in French, for receptionin tourist vehicles. This is known as the On Train PassengerVHF Service. It makes use of the leaky cable system providedfor the Shuttle Internal Radio System.

Produced and published by ELEKTORELECTRONICS (Publishing)

Editor. Len SeymourTechnical Editor Jan Butting

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VERY HIGH SPEED: TP208The TP208 is an interface cardwith a measuring speed of2x20 Megasamples/sec(8 bits) Phenomena shorterthan one millionth of asecond can still bemeasured wellThe completely digitizedtriggering ensures verystable triggering withmany triggerpossibilitiesThe TP208 has aninput range of5 mV/div to 20 V/div in 12 steps and an auto calibrationfunction Since both channels may be sampledsimultaneously, phase differences can be measuredvery accurately Even single phenomena can bemeasured since each channel has a32 KByte memory Comprehensivesoftware is provided

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8

DOLBY SURROUNDWhat is it? How does it work?

Based on an article by D. Laues

Acrilescription of Dolby Surround must ofecessity start with its background,

which is in film making. The production offilm sound is different from music -studiopractice, if only because it evolved separatelyand, for the most part, earlier. The film in-dustry developed facilities for recording,synchronization amd complex mixes fromseveral sound sources long before the firstmulti -track sound only reproduction equip-ment was developed. In fact, many of thesetechniques antedated the advent of mag-netic recording. When filmmakers could notfind equipment to implement those tech-niques, they invented and built it them-selves.

One of the most complex systems in thefilm industry was Cinerama (an early formof wide screen cinematography shot withthree adjacent cameras for presentation withthree projectors on overlapping panels toform a continuous picture and using sevensound tracks). However, for financial andproduction reasons, film makers looked foralternative systems.

Involvement of the audience is what filmsendeavour to achieve and it does not matterwhether the means to that end is dramaticor technical. Placing sound sources aroundthe audience has been used universally foralmost a decade. But the history of surroundsound started with the 35 mm four -trackformat, which had, however, a narrow andtherefore slightly noisy surround track. It wasadequate for loud sounds, however, and whenit was not in use, a pilot signal on the trackshut it off. Fims in 70 mm gave full -width qual-ity on the surround track, making it possi-ble to use subtler sounds and effects.

One of the systems to evolve in the mid1970s was Dolby StereoTM, which was firstused in the film Star Wars. In this system,the stereophonic reproduction is extended bya centre channel at the front and a surroundchannel at the rear of the audience. The cen-tre channel serves to close the gap betweenthe left-hand and right-hand channels; itmakes dialogue more intelligible and morenatural. The surround channel gives thesound a spatial effect. In cinemas the surroundchannel is usually reproduced by a numberof small loudspeakers that are placed in theform of a U at the back and sides of the the-atre. This system is widely used, because itplaces the information of the four channelson only two tracks of the film, which makescopying simple (which is, of course, impor-tant for the film industry). Moreover, it makesDolby Stereo fully compatible with nor-mal stereo, which means that films made inDolby Stereo can be run by a standard stereo

installation ( special effects are, of course, notheard then).

At the time of writing (mid 1994) more than4000 feature films use Dolby Stereo. Sincethese films can be viewed at home, either onTV or by video cassette, the Dolby Laboratoriesintroduced, in 1982, a system for consumerapplications: Dolby SurroundTM. This earlysystem was followed in 1987 by Dolby's ProLogic decoder, which is similar to the pro-fessional Dolby Stereo system as far as char-acteristics and quality are concerned.

How does it work?A simplified block schematic of a DolbyStereo encoder, used in the film industry, isshown in Fig. 1. It shows how the four chan-nels are combined into two film sound tracks.As far as signals in the centre channel areconcerned, this is fairly simple: they are at-tenuated by 3 dB and then added, in phase,to the left-hand and right-hand channels. Thesignal in the surround channel is also at-tenuated by 3 dB and then passed througha bandpass filter, which limits the frequencyband to 100 Hz to 7 kHz. It is subsequentlyapplied to a Dolby B compressor and then,phase shifted by -90°, to the right-hand chan-nel, and by +90° to the left-hand channel. Thechopping of frequencies below 100 Hz in thesurround channel is to protect the surroundspeakers, which are usually a deal smallerthan the front speakers and thus unable tohandle these low tones. The limiting to 7 kHzand the compressing provide the required noisereduction. Both measures ensure that anysibilant splatter caused by phase and amplitudeerrors in the centre channel are reproducedvia the surround channel (which would beboth unnatural and annoying).

Matrix decoderA decoder is required to derive the originalfour channels from the two film soundtracks. This may be an active device (towhich will be reverted) or a passive, so-calledmatrix, decoder. In the latter, the two mis-sing channels are regained mainly by ap-plication of sum and difference processes. Thebasic design of such a decoder is shown inFig. 2. It is seen that the left-hand and right-hand channels are derived directly from thetwo sound tracks, while the centre channelis formed by adding the two sound trackstogether.

The process of obtaining the surroundchannel is rather more complex. The dif-ference of the two sound tracks is delayedby 20-60 ms, so as to make it impossible for

Nan

,11

Ray Dolby was born in Portland, Oregon,in 1933, and received a B.S. degree inelectrical engineering from StanfordUniversity in 1957 From 1949 to 1952,he worked on various audio and instru-mentation projects at Ampex Corporation,and from 1952 to 1957 he was mainly re-sponsible for the development ofthe elec-tronic aspects of the Ampex video taperecording system. After he was awardeda Marshall Scholarship, followed by aNational Science Foundation graduatefellowship, he left Ampex in 1957 for fur-ther study at Cambridge University inEngland where he received a Ph.D. de-gree in physics in 1961, and was electeda fellow of Pembroke College. Duringhis last year at Cambridge, he was alsoa consultant the the United KingdomAtomic Energy Authority.

In 1963, he took up a two-year ap-pointment as a United Nations adviserin India, and returned to England in1965 to establish Dolby Laboratories inLondon. Since 1976 he has lived in SanFrancisco, where his company has es-tablished further offices and laboratories.

Dr Dolby holds a number of patentsand has written papers on video taperecording, long wavelength X-ray ana-lysis, and noise reduction. He is a fellowand past president of the AES (AudioEngineering Society), and a recipient ofits Silver Medal Award. He is also a fel-low of the British Kinematograph, Soundand 'Me -vision Society, the SMPTE (Societyof Motion Picture and TelevisionEngineers), and a recipient of its SamuelL. Warner Memorial Award and AlexanderM. Poniatoff Gold Medal. In 1979 he andhis colleagues received the Scientific andEngineering Award of the Academy ofMotion Picture Arts and Sciences.

the listener to determine the exact (sound)location of surround speakers close to him.This is essential, because the first wavefront must come from ahead, since that mustremain the direction of orientation.

The signal is then passed through a band-pass filter, after which a Dolby expanderrestores the original dynamics.

The main advantage of a passive decoderis the simplicity of its design. A drawbackis, however, that the design does not providegood channel separation. The maximum at-tainable separation between the four chan-

ELEKTOR ELECTRON ICS JANUARY 1995

DOLBY SURROUND 9

The Dolby Stereo trademark is used inprints and movie advertisements to denotea Dolby Stereo motion picture and is foundonly on pre-recorded VHS cassettes that em-ploy B -type decoding on the two standardlinear tracks Furthermore, Dolby Stereoonly appears on videocassettes or films thatare licensed by Dolby Laboratories. DolbySystem may be found on B -encoded cas-settes of non -Dolby Stereo films that werereleased theatrically in four -track mag-netic stereo or Academy mono. Therefore,no Dolby logo will be found on a video disc;although the LaserDisc is a high -qualitymedium, it does not employ Dolby noise re-duction. Similarly, while the linear trackson a VHS cassette might say 'Dolby Stereo',the 'VHS Hi-Fi' logo is not accompanied byany Dolby trademark.

Home surround decoders licensed byDolby Laboratories have carried the 'DolbyMP Matrix', whose exact meaning was a mys-tery to most people. Tb remove this mystery,and to indicate the presence of DolbyLaboratories on the growing number ofnon -Dolby B home video formats, a newtrademark, Dolby Surround, was intro-duced. The new logo appears on licensed de-coders, replacing Dolby MP Matrix, as wellas on all forms of video release, includingthe non -Dolby B stereo formats such asVHS and Beta Hi-Fi. Thus, Dolby Surroundindicates the presence of stereo audio withsurround information recorded and en-coded with a Dolby DS -4.

Obtaining the Dolby Surroundlogo meansthat a manufacturer adheres to the basicoutline provided by Dolby Laboratories. Ingeneral, licensed decoders have to contain:

Metered input calibration to optimizelev-els for different VCR and videodisc out-put levels.

A basic L -R surround matrix to extractthe out -of phase surround information.

A delay line, not only for time coherence

00

00

DOLBY STEREO

DOLBY SURROUNDPRO LOGIC

940059 11

ofinformation that isboth in the surroundsand front speakers, but also to reduce theperceptibility of unintentional surroundleakage, especially the sibilant 'splatter'sometimes caused by azimuth errors.The recommended delay range for homedecoders is 10-30 milliseconds (DolbyCinema Processors are adjustable from30 to 100 ms because of the larger front -to -back size of motion picture theatres).

A 7 kHz low-pass filter. This is the high -frequency cut-off chosen by Dolby Lab-

oratories to prevent bothersome hisscoming from surround speakers m the-atres during quiet or inactive periods Therelatively steep HF roll -off also helpsreduce delay -line noise and rear-than-nel sibilant splatter.

A modified Dolby B -type decoder. L -R mas-ters contain this modified B -type de-coding on the surround -channel infor-mation to aid the low-pass filter in noisereduction and masking of sibilant break-through. It should be noted that the twotracks on a Dolby StereoL-R always em-ploy A -type noise reduction that is de-coded at some stage prior to video cas-sette duplication. The modified B -typedecoding remains on the surround chan-neL

An output stage with a ganged masterlevel control.

Even though dialogue (speech or music) inhome stereo playback seems natural corn-ing from the phantom centre, many believethat the addition of a centre speaker helpsto lock the dialogue to the image on thetelevision receiver, with benefits observ-able even on 19 -inch (48 cm) sets. In largeliving rooms, especially, a centre channelcan help stabilize the dialogue (which isalmost always in the centre) for those seatednext to a front (left-hand or right-hand)speaker.

nels is shown in Fig. 4.

Pro Logic (active) decoderAnalysis of the output signals of a matrixdecoder shows various weaknesses: the twomain channels contain information not onlyfrom left and right tracks, but also con-

stituents from the centre and surround chan-nels, since these have not been filtered out.Moreover, the surround channel contains con-stituents from the difference signal, whilethe centre channel contains parts of both theleft and right track.

It is clear that the main task of an activedecoder is to improve appreciably the chan-

left

centre

surround

right

- 3dB

- 3dB BP

left-hand

track

+90"

Dolbycompressor

righbhandtrack

940059 - 12

Fig. 1. Simplified block diagram of a Dolby StereoTM encoder.Note that this is used only in the film industry.

nel separation. This is why it is provided withdynamic direction compensation. The ProLogic decoder analyses the composition ofthe signal as far as phase, amplitude and fre-quency are concerned and generates thenecessary correction signals. If, for instance,at a certain instant the left-hand and right-hand signals are identical in amplitude and

0'left-hand

track

right-hand

track

A t k BP HO.1

left

centre

ex=e,surround

right

940059 - 13

Fig. 2. Block diagram of a Dolby Matrix decoder. Note that thisalso is for use with film sound tracks only.


10 AUDIO & HI-FI

phase, the decoder rightly acts as if thismono signal belongs in the centre channel.It then increases the gain of the centre chan-nel and lowers that of the left-hand andright-hand channel to ensure that the totalsound volume remains the same.

Active decoders usually have four volt-age controlled amplifiers, whose gain is ad-justed by the programme material. This se-lective amplification increases the channelseparation between the main and auxiliarychannels from 3 dB to 35 dB. Although someperfectionists feel that this is still a low fig-ure, practice has shown that greater chan-nel separation is not necessary, since the fourchannels form a unified sound source.

The block diagram of the Pro Logic decoderis given in Fig. 3. It shows that the basic ma-trix and preliminary processing of the sur-round channel signals are identical to thoseof Fig. 2. An addition is the dynamic direc-tion compensation which controls the fourvoltage-controloled amplifiers (VCAs). Inthe very latest types of decoder, the entiresignal processing and compensation are ef-fected by digital levels. The audio signals areconverted into digital levels by an ADC (ana-logue to digital converter) and processed bya signal processor and suitable algorithms.Filtering and gain control are also by digi-tal levels. The signal delay of the surroundchannel is effected by DRAMs (dynamicrandom access memories).

The channel separations obtained witha Pro Logic decoder are shown in Fig. 5.

Domestic surroundAs mentioned before, since Dolby Stereomakes use of only two sound tracks, thesound may be reproduced by any standardstereo installation to which a decoder andan additional pair of loudspeakers havebeen added. This compatibility with stereois perhaps the strongest point of the system:it enables the pleasure of listening to sur-round sound to be removed from the cin-ema to the living room.

Apart from the fact already mentioned thatthousands of feature films have been madein Dolby Stereo, there are many CDs avail-able with original Dolby Stereo film soundtracks (continental Europe: 300+; UK 1000+;USA: thousands). And, of course, many of

0 left-hand

track

right-hand

track

0

At BPDolby

expander

VCA

VCA

VCA

VCA

lett

centre

surround

right

,0

900059 - 15

Fig. 3. An active decoder provides dynamic direction compensation, whichanalyses the signal and continuously adjusts the output levels of the

four channels via voltage -controlled amplifiers (VCAs).

these film are shown on television. As theTV stations broadcast the original film sound,this can be reproduced in the living room.Consequently, there is a plethora of suit-able decoders available from all self-re-specting manufacturers: Denon, JVC, Pioneer,Sony, Tshiba, Yamaha, and many others.Prices are coming down, too.

Most of these decoders have a number ofadditional features. Often there is an inte-gral noise generator which is useful for ad-justing the levels of the four channels. Anauto balance compensates for differencesin output level of the TV. And, of course,there is the inevitable remote control. Somedecoders also have provision for connectinga subwoofer: the necessary cross -over filteris already fitted in the decoder. Whether asubwoofer is required depends, of course, onwhat speakers are already available with theexisting audio system.

When buying a decoder or decoder/ampli-fier for Dolby Surround, make sure that theunit carries the original Dolby logo precededby the two mirrored Ds and Pro Logic un-derneath it as shown on the preceding page.Whatever the salesman tells you, equip-ment that is not so fitted or which carries anincomplete logo is suspect and should not be

> 40dB

LEFT3dB

CENTRE

> 40dB

SURROUND

43dB

RIGHT

900059 - 10

Fig.4. The channel separation provided by a passivedecoder is not particularly good.

bought (at least not for the present pur-pose).

LoudspeakersA typical loudspeaker array as used in cin-emas is shown in Fig. 6. To the main speak-ers for the left-hand and right-hand chan-nel have been added one or more speakersfor the centre channel and a series of smallerspeakers for the surround channel at the rearand sides of the theatre.

The setup in a domestic living room is rathersimpler as shown in Fig. 7. Two small speak-ers for the surround channel and one forthe centre channel in addition to the exist-ing stereo speakers are normally sufficient.

There may be some confusion as to whattype of loudspeaker should be used for thesurround systems. A number of manufacturersoffer special sets of speakers and many peo-ple will wonder whether there is a need forthese. The answer is yes and no. No, em-phatically no, as regards the main speakerswhich should be standard hi-fi units: normallythese will be the existing ones. As far as thesurround channel is concerned, the usual hi-fi speaker is really too good for this, since thefrequency range is limited to 100 Hz to 7 kHz

> 40dB

LEFT CENTRE

> 40dB

SURROUND

> 35d B

4,

RIGHT

900059 - 16

Fig. 5. The control system of an active decodersubstantially improves the channel separation.


DOLBY SURROUND W

Look what's new inversion 4 of SpiceAge forWindow sTm

DDE link with Modelmaker, theutility that synthesizes opamps,transformers, attenuators andtransistor library modelsReflection coefficient analysisNoise analysisImprovements to digital displaysAuto -time interval setting optionTime optimisation in relaxed circuitsFaster quiescent calculationsSPICE repertoire enhancements forASICSBetter screen & paper presentation

Ells graph Network

seem

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on 0 to A converter circetit

Spiceage-c:%spiceage1netstrichil.cmi)Analyse Frequency

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110

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00,00

111111

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641/0/ I/1 .0001

100

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100

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Reflection coefficient

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From as itt e as £100incl VAT & postage

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Help

86.6ra ,, e4e4rwa we - 0 r.1 h 4. .0 1., /

Windows' wave (.wav) file compatibility. Multi -media users can listen to their waveforms or capture soundsamples for Fourier analysis or filtering. Binary output option makes ROM programming easy.PWL non-linear enhancements saves calculating polynomial coefficients for those awkward functions.

Make sure you know what you are missing by asking us for a copy of the demonstration program and booklet.Subscribers to the SpiceAge maintenance service will be receiving their new version along with a copy of the newmanual.

Please contact Those Engineers Ltd, 31 Birkbeck Road, ---

LONDON NW7 4BP.Tel 0181-906 0155, FAX 0181-906 0969. Mogragwe OM.

4AY/

A A. A A.left centre

surr and

Aright

940059 - 17

Fig. 6. In a cinema the additional channels are usuallyreproduced by quite a number of loudspeakers.

(why use an expensive speaker that goesdown to 40 Hz or even 20 Hz?)

The importance of the centre channelmust not be underestimated, because thisis a real pillar of the Dolby system. Filmmakers correctly maintain that the centreof the sound of a feature film contains muchinformation, since there virtually all dialoguebetween actors and actresses take place, aswell as much other action. It is at this cen-tre that a standard stereo installation pro-

vides no reproduction. Add to this that in mostcinemas the left-hand and right-hand speak-ers are (of necessity) far apart, and it is clearthat many viewers find correct localizationof the sound impossible.

All this is, of course, not terribly impor-tant in the living room, but it illustrates thepoint that the speaker for the centre chan-nel must be of reasonable quality, althoughit need not be as large as the main speak-ers, because it does not handle so much bass

left centre

)3?.. surround

Aright

940059 18

Fig. 7. In a domestic living room, to theexisting loudspeakers can be addedan additional speaker for the centrechannel and two small speakers for

the surround channel.

power (-3 dB with respect ton the mainspeakers-see Fig. 1). The best pplace forthe centre channel speaker is near, but nottoo close to, the TV set. If too close, the mag-net of its drive unit may adversely affectthe TV picture. Note, however, that there arespeakers available with magnetic screening.

Next month's issue will include a DIY decoderfor Dolby Surround.


m Please mention ELEKTOR ELECTRONICS when contacting advertisers

:1:11.11 0 11111111111rill

9338

INTEGRATED

VICOM G FAX 081-552

CIRCUIT SPECIALIST

0946

74H0589 1927450590 1.2074E10592 1,247450593 1.897460595 1.147460597 1.1074HC620 1.827480623 1.4879190623 POA7460640 13674HC643 1.3674190696 1.86

74401237 1.2074H C7238 0,6974507240 15374601241 0.58741107242 1.2474407243 1.2474H04244 0.5474604245 0.5474504251 1.1174601253 1.1172101257 1.11745C4258 1.11

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0.600600.601,101002.060940/20.98PO4(7980.98

7912E4 0.7879157918

0.440.44

7924 0.44794125 0.24791205 0.42796105A 0.5279012 0.44790124 0194480507 3 404494075 60.0LM317MP 0.98

354/11300/Sqr 2.98KBPC1002 1 64KBPC3502 2.98W005'147501/ 032W020-1.54 0.402W02 0,02998105IS1L 0.6624851208/31. 0 70138001500/ 013135B8001500014 0,600116008/60A POA04060081604PO4

Freq.. MHz11.11-2 28.90 ee

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4,46152,6,8.9.63

10.12.1"18.432, 19.8608,

29' 24, 29 630MH

Price. E3.52 ea.

32. 32793, 333408 50. 66MHz

19M44025622.10 69595944647.16 4.60m80644661649651: 162:

NMC37645.15 1.60UP D414540-12 4.20

UP041464C-15 4.20072416C-2 9.00UPD416C-3 3.650704460.1 260

STATIC RAM

TEL 081-471

DIGITAL

TLX 929709

74710698 1.611 74607259 164 74F64 1.24 7440573 1.38 LM317T 0,78 CRYSTALSP''''' MAS4000 5061,5 45108 154 401664 143 74175 1 7445189 2.81 7410693 PO4

7460651 1.497450652 2.40

74807273 1.24741407280 1.29

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0.312.24

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LM33810 40.5LT1084045 6.52 HC49( HC18/18 "' 2114.3L 3.40

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118451280.18

45118 0.440A6

45138 960

401781 678401881 0.76402087 0.95

741807418474185

1.167440190PO1.76

0.547940191 1497440192 0.54

741679474407957415796

POA704POA66222556123127450608 POA

74160659 POA7460684 POA

74607283 01474501297 14874601299 1.68

7478674710974F112

0.340.580.63

7450648 POA LT1085045 6.606041955 2,4014783060 6.98

7195. MHz1143200 1.60

2000000 1.66

programmableCrystal

OSCillators

626417.12 2.404.95

25 LP 10 4.957400074002

0.500,50

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40028

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402187 0.135

492381 0.380.713

7410174192

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7450665 POA74140670 1.16

74004354 0.7474507356 1 54

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2.453200 9.962457600 1.49

EX0-30 SERIES8pin DIL Plastic

006161165E3 590COM6117AE3 9..85

DIODES

40069 042 45168 0.44 402497 74193 1.65 74401944 a54 81459548140975

1,251.25

7460677 POA 74507365 1.28 747125 056 74008 0.50 3.276800 0.98 Package HM1-6116.5 4.381529866E118,204007UB 0 2445178 1.64 4025131 0.38 74221 2.40 74401955 0.56 741-3676 POA 74501366 1.34 74F126 705 74010 150 3.579545 Freq =MHz 145311165 9.60

44C SERIES4005040095E

0.42451580,26741600045188 0.44 402751 DAB4028E1 0.56

7925974265

2.921.46

7940196 POA7445221 0 46

74710680 1.057450682 POA

74501367 0.5974504368 1.29

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153881 2.541839975,, 6.55

3686400 1.024.000000 I.

12, 14.31518, 18.16.384.19.6608 8

596716LP-2 2.601112611617.3 2.60

7460020.22022000078 .228452013 0,44 402961 0.88 74273 POA 7445224 10.30

7480684 POA 74504373 0.52 747139 058 7'039 0.90 15 001 0.04 4.096000OMHz HM611741,3 5.75

4010B 0 29452180.84 404081 0.78 74276 5.18 7413240 0.48

74HCO3 0.28 7450669 0,74 74601374 0.52 747198 POA 74032 0.50 154002 0.04 4,194904 1.HM6225611.10 7.93

4011840110640124E401284013B4014B4400115689

0..29452200.28020452780.220,22452950.4245308

2451180014284532B

0.6645268 0.60

45288 0.491742 89- 5 '1,1874403

4042E17 0.744096131 1.41404787 1.06404984 1.064050(34 0.484051ST a 78405264 084

742797428374298743657436774393

POAPOAPOAPOAPOA4.89705

741.0241 0,487445242 POA7411243 0 50744320.1 0487410245 0.507411247 POA744S248 POA

746004745000474000574600774500874600974H010

0.220.240320.480.220,480,29

74190690 1.627460691 1.827460692 1.827480693 1.827460696 1.827450697 1,327450698 1.82

74HCT377 0.6574504390 0.6874601393 0.6874501394 POA74504423 0.8274601533 1.6374601534 0.75

747151 1.47747153 158747157 0.58747158 0.60747160 0.90Programmable7471604 POA747161 0.88

74042742487407374C74740767408574090

1.781.541.680.891.14

1.881.18

194003 0.04184006 0.04154007 0.04154148 0.031N4149 0.06154150 0.08104446 0.06

4.4336194.6080004/152005100000/5 1.5.068800 1.10Package5.242880 7.205,888200

Price: 03,92 N.

pin D1L PlastIC

for57 DK Frequency

HM626444P-12 3.95695264AS/20 3958502677.35 5,07919628128LP-50

18.55HM662041.12 15.80

4.95

4016004017840188

0.260.38450580,4607440010,2,45396

0.6842300 /82

0.600.62

4053,1 0'98406087 184486601 0.594068E31 0,38

406929T 13,407081 am

74423 POA 7445249 POAKM622513ALP-1074L0256 POA7440257 0.0074402574 048

74110117411014741-1014A7440207471021

0.220.260.380.240.24

7450699 11274604002 0.48741904015 1.0774604016 158746C4017 0.60

74504540 0.6674501541 0,7474507563 1.4674604564 1.6774607573 0.74

747162747163747164747166747168

POA0880.88312POA

74C9974015074015174C154740157

1.833.48POA4.883.02

1947284 0.261N4735A 0.241547365 0.241547404 0.241547434 0.241947446 024

6.0000006.1440006.400000 1.546.552000 1.406.553600 1.21

E PAT S. AA,

6,6086409N.000310 /MHz

LH51640.10L 2.40

70051017 3.30UPD43256AGU1OL

UPD43256C.12 5.60

741.300

744002

0.180240 198.33

40204E4020B

036454190.38741.0047462309-6945438 0.574071131 0.35Wiz741103 olza

1.00745027 0.24

0.24741104020 0.5274504022 174

74607574 0,7474607583 1,48

747169747174

3.600.80

74C164740221

1.91

214 0.24I

7.372800 0.788.000000 190

SPG8640CN08684.1t10070,5 UPD4364015 470

4o21B 0404944 8 a" 407581 638 74L.505 021 74452584 0.48 746C32 0.24 74604024 0.62 74601597 1.52 747175 0.80 740240 1113

894756252268 0/9 8.867230 1.34 IR/PROMS

4022B 140 r4.5470 3 26 407764 0.38 744506 7410259 POA7471042 0.54 749104028 0.58 74507640 114 742181 615 740244 1,38 1552328 0.09 9,830400 1.20 SPG86508N

4023B40232840244540248402584025911340268

0.201A54980,231300.320.2403079LS12094

7.00.6518 402g 6,995" ---

554B POA555B 0825568 0.820078 1.98

4078E31 0.38408161 0.384053137 0.45409487 0.95

430857 "54,100-1 1.024511131 1.35

0.6

741.30774400874L50974151074LS11

74LS13

0 .

0.

7445260 POA7440266 POA7440273 POA7440275 POA270256-157411280 0.667410283 0,457445290 POA

7450517411058746073746074744274A7490757491076

0.320.540.360.280.280.480.98

74504040 148745C4046 1.447450404641.9074604049 0.46741104050 0.3874804051 01474604052 0.74

74501643 1.9774504646 2,4074601648 6.4074HC4651 POA74507652 P0274501670 1,1074501673 POA

747182747189747190747191747192747193747194

POA4.40POA2.92P062.921.36

740373740374740901740902740903740906740907

1.381180.940.94POA0.940,54

15523413 0.0915533713 0 481553498 0481593525 0.461553578 04111453658 0481653668 0.48

10.00000 1,1010.6990011 0000012.00000 0.9213.87500 2.4014.00000 . 414.31818/S 0.8S

0 00083 to 100042

PX0.6000,005 ro 600k42

820.10300,0083 to 1MHzAll above

09.25Price: 5 325 42

270128.25 3.95270644.15 3.95

3.9527025625 3.952705120.12 5.4827010002.12 8.92

27C-1096.12 POA402764028840298403084031B40328

0,300.380.350.3474110931.24

0.70

5699 '5000 1,62

5618 1.96'

0628 5.132

56613 1.10

5668 5,02

45148445166/7451881452001 1.7440295452187 1.

74L514745515741.52074LS2174LS22,a, g

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0.200.240.68

7440292 14,587440293 0.427410294 P265270697P-20T7445295A POA

745077746085746085

741601077490109

0.520.520.300.460,48a46

74609053 0.747460400351,12741404060 0,4674504061 PO474604066 010746040665 0 59

74601688 1.10746074002 0.39745014015 1.41745014016 052745044017 0.687411044020 174

74719574721974722474724074724174F244

2.00POAPOA0,600600 60

740908740911740912740914740915740922

1.5113.9813.980 942.24510

1553708 0.4811653800 0.48155401 0.11195452 0.111146287A 1.5515825 2.75

14.74560/6 1.1014.74560 1.101560000/S 1.1016.00000 1.021800000/S 1.2019 43200/0 1 10

5(008801550.00083 to 101479Cal Tol. 5PPTIPdce: C 10.50 e4.

UM 2721016-20 060199270102411010

16.633 40

HN27C64G-15 4.20

8527°94240 "aDC to DC

co "6"0403384034B40356403E940378

0,8811074501130.527410282 981 277460125

8452264"8 40457243 0945737 6.9.5808 804

5918 PO45828 708

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452884453980 P45388T 1.05741.0322454181 1.

454301 1

745526741.327

74LS30741531

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0.200.200.24

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7415298 POA2'9'92" 1.76740925741321 329

POA7440322A POA7415323 POA

7450112

745012374801234

0.501541420.420 42

74604067 4.7274504072 0.4874504075 144745C4078 146741-104094 0.78

7411074024 0.68746014040 0.70745044046 2 10745074051 0:96745014052 0.96

747245 CI:66747251 POA1.607472514 0.75747253 PA747257 705

740923

74C9267409298009580098

6.288.40140POAan0/8

15825A 2.7515827 3.14100252 0.205082-2600 0.6650132-2810 1.405082-2835 0.44

19.66050/S 1,2020,000003HN462532P22,11840/0 1182410000/0 I. .527.64800/5 1.2030.00000/5 6.99

4.501-11448271286.85 4.55659827645 3.80m2716.171 3.50

40

TDK 0E-0344 5.603W59 15.15 2760IF% 0.010 23.40

44003313:3

40/45B404104041UB

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0.420.480 48

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7441L.N35838 1,386649 5895858 174007g 0 00

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45,5,1 0059010687 0,5340244131 1,35M614270256.30741337

744038741040

7445347 708

7440352 POA7440353

74501267460131746013274501337460137

0.450.520.600.44an

74604316 0.7474604351 1.0579504352 1.62748C4353 1.6274504511 0.89

74501'4053 0.84746014059 2.24745074060 0134745074066 0,667414014067 5.78

74F257A ass747258 POA747259 POA747260 0.76747269 5.54

44115 0.60A4144 0.72

AA27,AAZI7 8AAZ1E3 0.48

32.00000/S 1.4048,00000/0 1.68S 9 Series

HC33/U

1 Watt OC/DCEV Input .Output

DIL S L& I byNewport

51/A0505,5V

4,595LL.;7764,132K 0:30

WM27064.20/2104.90

19.131.927C128.30 9.2D5.10

74S SERIES7450074002

0.680.68

4042840438

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0.322.11 7440364 POA

741601387440139

0 34032

74504514 4 1074604510 1.85

745044075 0.36746074094 0.84

747273747280

0,960,70

7400374504

0.78168 89919 9'99

0.20.,500

.0.3072006 9951450509,4.- -50405129127

HM02702560,254.95

72013 P05 74 SERIES 741.547 0.68 74'2299 0.5374133654 0.54 7450141 POA 741104518 0.87 7 CT46 4316 0.88 747283 1,00 79308 0.68 4.98

BAIN621.000000 3.95 59605159159 500270640-25 3.66

40461340468

1.

0.447201 POA

7238 PO47248

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74403666 702

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746074351 1.047471014510 1 54-

747299747323

POAPOA

7450974010

0.681.70

841/450.

5585686204 0.32

1,843200 3.712.0001300 4

Price: £ 8.654.. MS2516J 4.5871.1027128.34-25 4.80

4047640451340459

0.440.820/0

791VP 9-80737VP 19,60

73887 1914

7402 0.327403 0.327404 0.34

749051741.554741.555

0.220.280.

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746015174601537460154

0.400,420.62

74604538 06874604543 0.9874607001 1.01

7416014511 199745044514 1 64

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2.557152 3.71

6457600DC/DC Converters

by ComputerProducts

Th327161:45 4.600R0272560/217 5.60uPD27324/217 4.95

4045409050B

0,28028 ' 7501/0 2' 50

7405 0.347906 0.613

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0.30.79 791.136t32 POA

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7403874040

0.680.25 01179 0.42

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PN1823 24.600671 26.70

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POA

7408 5.377409 0.387410 0.35

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16074601617450162

0.740.420.74

74507240 0.9874607241 0.9874607244 0,98

745047007 0.39745077038 5.4074H077046 2.80

74736874F373747374

PO40.600.60

743647457474666

0.360.830.83

9 ' 961 230 3.98evv28-100 ass91932.8° 1.60

1079545 1.".

5 068800 2 257.864320 1.45

P519" 4200PM951 41 50 EEPROMS

RESISTORS4055B 16 0097 0.68 7412 0,64 74LS76A 1.05 741-5378 POA

74110163 0.42 74507266 0.66 741-0440102 2.43 747377 1.34 745112 0.90 CV8005 0.6013.000001) 1.14 28064-25 9.80

40560

40601340658

0.83150.380,50

°°98 an0100 POA

0191 POA0102 1.96

7413 0.767414 0.547416 0.487417 0.48

794.37774LS7874LS8374LS83A

0.449320.391239

7440379 1.5074403815 POA7440385 P0-7440386 PO4

74 0164798016574501667460173

0.420.55

80 80.28

74507292 1.1074507294 1.1074 C75 640 1.9874407643 1.98

74140140103 1.48746C440104 PO4

747376747361747385747395

2.725.70POAPOA

749124748132740133740134

3.131.11

0,802.15

0016C 0 40'

MV1404 15.90

Ply"05205 0.10

10 00000 2.251 1. 05920 2.4012 00000 1.14

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14 00000 2,25

28064-15 10.9580255-20 1840

280256.15 19.60

METAL FILM0.25W 1%E24 5e.ies7411C SERIES

SURFACE40668 027 9193 1-14 7420 0.37 741_5E15 0.36 7410390 152 7490174 0.42 74507645 1/9 MOUNT 747399 POA 745138 0,97

607,6, 0 0n-65-0. -.50. '16.00000 1.14

1013 to 1141 280256.1500 28,505.10

40578 228 0109 POA 7425 1.10 791.586 0.26 7440393 0.42CI 006 7480401021,32., 747412 POA 740139 0,97 0447

20,00300 1.52Pack of 5:. 85p 0281640

028165225 5.100.320.32

4068640694/13

o.0.22

0106 0.320107 0.42

7428 0.487427 0.59

74L590744591

0.32POA

74453/5 POA4HCDOM746011317460182

1.94019

7471040192 L12-460029746040105 1.42.48cm.

74741374F432

POAROA

745140745153

1.021,39

0690P6KE365 0.8 8 24,00000 1.90

Pack 8310 9 25pX21364AP.35 12.20

40709 062 0199 P0A 7430 0.35 741.092 POA 7460190 0.89 747521 1 740157 1 09- P68E47A 0.88 UM.1METAL FILM 24001 1.82

744CT SERIES40718 022 0109 1.24 7432 D.45 749093 240 7415550 POA _1.1 0,68

46004M 747524'

PO0. 743163 2.79 REC52A 0.40 PRECISION 24032 2.10

4072940738am,40788407794078840815

0.220.280,22

0,640.280.280.22

0770 1.62

01 3.400116 POA

0117 POA9147 1.23oleo 0-929181 0.54

7437 0.547438 0.467490 0.777442 0.547445 1.127446 1.387447 5.98

741.69574LS967490107744010757440109744510957445112

0.400.820.330.780.330.660.33

7440399 0.927445423 0.987445445 P057440450 10.6874404614 P0574-04°3 4.187445467 POA

7460192

' ' 7-741101947749H6C195

6C221

774080070

0 78o'7,- '0 780.780.56

0'760 04-

7450402 0.247440703 0.287 4HC704 0 2474710708 0.247440710 0.24245030M7450411 0.24'

450004411008M44010045014M O.

460209 00.88

450320 0.98

74753374F53474753774F53874F539747540747541

POAPOAPOAPOAPOAPOA1.98

793174749175743182740189

,

745195748240740241

1.01,.493.622.3530062.642.31231

2PC.2 71/ 0.06

ZENER DIODESMISC.

9,Y8007V98.6002193015 610

ap 2.2,

5.192000 2.021900000 22511 00000 2.2512.28800 2.661500000 2.25, 7 73447 2.80

0.25 WATT 0.139696 Series

1050 to 255KPrice 00.94 each

HIGH PRECISIONNON -INDUCTIVE

4004 29824016 0.4028004A.20 4.40

59C11 1.441.72

=45 12893256 1.52

0162 0.72 74478 1.40 74401125 0.66 7440468 POA - 75T-7460240 -0.46a7460114 0.28 450744 0.36747543 a57 740244 1.95 921930196690 1E400000

WIRE WOUND 93058 2.16

4088840866

0,560.560174

9183 0.720.42

7451 0.577454 0.72

741.611374151135

0,360.42

7440469 POA7440490 POA 50241

744502420

0.987450421/460720 0.28

0,23450750 0.3441-1085WM 0.85

477 544747545

PO4POA

746257745258

1141.34

82793020 6.60____2100000191.30247610 21.00000 2.25

0.15 WATT 0.1%MISC. MEMORIES

4089B 0.980175 0.42 7470 D.54 741.3114 0.38 74404914 7027460243 O.

7450127 0 28' 480669 0.313 747547 POA 740260 0.77 8219303366,60 24,0000 Temp.00e5.3ppm

40935 0,26 0181 POA 7472 3.38 74151145 0.40 7410540 0,807_ 450244 0.48 7450430 021 41-10123AM 0.46

747573 2.79 740273 2,68 'Z13130120 0,74 IOR.50R.100R,250R, 341.1J 0.58

409413 0.38 9 0.62 7473 0.56 7440122 0.33 7449541 aeootr1 245 248 7450432 0.29 4601250 0.46

747574 2.78 740274 2.86 82461C9720.09 CRYSTALS misc. OK 1000 AM2148.4500 5.44

40950 0.700199 0.740194 POA

7474 953 7440123 0.35 7440569 POA7948573 1.02

74502454 0,54 74140142 0.48'7460173 0.38

4501329 042460138M 0.38

74E579 6 59 740280 196 B26610241/0 09ZENER * 4C4317

Price: 03.85 each A9270261P0 3.98IC1713095-100P 10.40

408684097B40988

1.10235084

0195 POA

3240 POA

7975 D.647476 0.647480 1.26

7945125 0.2874401255 D3274LS126 0.32

7496574 1.027440590 5.09

74502517 246025; 3

4710257

936

0'520.52

7450474 0.287460775 0.38

41-10139M 13845015477M 0.64

747609747620747621

559POAPOA

74528374037474S394

299211211

DIODESHIGH400mW

1900000 6.99

MINI CYLINDER

PRECISIONNON -INDUCTIVE

11713242100P 12.201089,4e 0.95

40999 0.420244 1.36 7,83 L., 0 74901265 0.40 7440592 5.09 7460258 0.73 7450485 0.54" 4401670 0.38 747623 POA 745912 2.31 24710 757 0.032768 0.98 WIRE WOUND MCM4027AC3 2.80

4104P41065416013

1

0181.40

245 1.36

257 .9,'1373 '24

7485 0.587486 0537490 0.72

744013274901337490136

0280.350.78

7445593 7.12

741-7449597 5.20

74502597.110266

0.520.480.54

6 0.317450487450493 010741107107 0.41

45C161M 041-10164M ,

480165M 0,57747821

747646747676

1903 22704

Pm' 60 each

ZENER DIODES

WATCH0.032768 082

0.33 WATT 0.13s

ap 8,'7/98,5"64P

0020095 POA0E1201266N 2.4958201535 5.80

VOLTAGE

REGULATORS78006AP 1,157805 0.447805A 0.627805E4 0.68

CRYSTALOSC. MODULES41618

416313

4174941759

1,201,201

6314 0.346926 P0.

0027 5.99

5026 POA

74904 0.727491 2.567992 0.677493 0.60

741_51377440138744013974401395

1.580.340.400 42

7440621 POA7415622 POA7445623 POA7940624 210

7445027974110:

7450280

-7450294

0..90

-1

'

74607109 0.4174601112 0.4274504123 164-450221AM741401125 0.56'

46017312 0.4846C1749 0.38

0.65450240WM 015

4782374782574F027747841

POAPOA3,323.51

.,010010V421 LI 2007Pose. 6s. each

;CO'Re2"0. R RPrice'8.05°0 582518155 6.08141406504J4 9.4050093085 145751011-1 3.909pin 1314 1006,7206. 2506,

4194644139P 11.05

5040 POA041 POA

74935 0.607497 4.48

7440145749.0147

0.66POA

7440625 P0

241-9092° '

74140298450299

9781,38

74601126 0.54:450244MA741101' 32 151

0.55450245/9W 0.62

78067809

0.66962

ZENER DIODES1.3 WATT

Plastic pkgTTL Output

50019,10. 20, 514104,2019

T8718003014 7TEM24S10N 2.90

74AC SERIES441094411P

.6,4521.58

5199 1.5801" POA

74104 0.6774107 260

7440148744.0151

0.870.35

2415.'27 POA

74(-062°74603237480352

1.827 20

74501137 0.54'460251M74504138 0.31450259M

042169

78067812

0.820.44

2,71 to 2007Price each

4 Pigs spaced atcomers of 800014Freq.. MHz

Price: 0,10 0000 11382400.10N 9.15130501P 3,50

744000 0 38MEMORIES4412FP POA 0109 POA 74110 POA 7445153 0.36 74L0629 225

7440631 POA 7450353 '0.75 74601139 0.52 4110273WM 0.5541-1C367WM 0.53

745002 149 78122 0.55 0, 4,9102, 3. 10,105509AP-2 350705517AP.2 4 20

44121/74416P4419P4429684433P4448p9447P

7061705popP09.804pop.POA

5145 13.965146 13.96

°Th1P° 18 4,91007218-4551057413'0,01067°1' 9,5157P211'05

74116 3.1074118 POA74119 POA74121 1.4074123 0.8674125 0.6474126 0.98

7440154LS15

744215674461577445158744016074451605

1.23

0.380.420.30

0.520,60

7440639 POA7445640 POA741640.1 2.797445641 8057440641-1 2877440642 POA

74403547450356

HI -103.65

74 0'967460367708,000 --5.07450373

o 8,,,.

0 840.52

0'

0 .

74507197 17174601151 0.5274601153 0,5174401154 1.20'4501157 045/4504158 0.51

74601150 0.54:

4710373WM 0.55411C379WM a554403900 ° .'4603939 0.03450540WM 17645C541WM 0.76

7450047450087440107450117440147421320745032

0 40'140

0.400400400,400.40

176 57818782478L05784068--781.12781125

0480,480.480.240-290.240 28-.--

ZENER DIODES3.0 WATT

7.57 to 2707p ' ' 5091747 9.39'ZENER DIODES

WATT137/ to 200V

12. 16 & 20M67

24.32.90660MHzPrice 63.94 ea.

Spin OIL

C5565P4-15 9.807904014J21. 3.40

RESISTORS SODOHO to 3123

Case 1206 -Pack of 5Price: £0.30 per pli.

DYNAMIC RANI

4164-10 1,40416412 1.204164.15 1.2041256.8

4407p14468P

7,206.94

5' 05P° 11.0,5159 POA

74128 1.4274132 0.86

74401617411161A

0.460.49

7411642-1 POA7413643 POA 748°2747460275

0.460,7874601162

745 C4161 0,540,84'

4HC573WM 11941-10574WM 0.84

7450747440109

048054

7841575L24

020.26'

Rrice.420 eachSealed Metal

Package41256.10 20041256.12 2.40 CAPACITORS

SURFACE MOUNT44696 pop 454°3P POA 74145 1.10 7440162 1.10 7413644 P05 7450577 9 74501163 0.54" /1.10688WM 0.84 7440112 181 784513ZENER DIODES HCMOS Output 41264.15 224

44897 po 494°6P 3.58 79150 1.86 7411624 1.10 7440645 0.68. - --- 0

384504164 0.5224604017M 0.48 74501313 165 78M05 042 STUD MOUNT 41464.12 4.45

4.8045407P 6.47 7,51 0 80 741163 040 7445645-1 2.79 7450390 74504165 0.52". 45090200 0.48 7440139 165 786905A 242 20 WATT 13.2rnm sq. 41464.10 4.45 Molthayer Ceramic44%7 6.98454117 708 74153 0.90 7411634 0.64 74L0646 4.65 70.(op00 0

'

68404166 0.52 44040400 0.44 7450151 058 79M12 0.42 7'5V to 750 Pins spaced at 4464.10 2.80 63 VOLT04070 5.28454147 704 74154 220 7440184 0.40 7448652 POA I Nu423 0.5474507173 0.52' 41104046M 156 744C153 0.65 789122 0.42 P1:00' 64'94 99-

0e11rere of 8pinDIL 914258A-70 3.50 Case 5106 12064499P 6,98 74155 0.81 7440165 0,50 7411669 1.58

74089108174604174 0.51 4504060M 0.48 7490057 0.01 781113A 0.98 BRIDGE Frac - , MHz 44025622.10 5.95 0/L221.25mrn

4000 SERIESSURFACEMOUNT4501U13

450290,44

9."

74157 0.7474158 1.57

74199 "9

7445166741_9168

74L2' 69

0.50POA0.50

7440670 0/874L5673 POA7440674 16.89

733' - -

7450534745C540

0 980.980.69

74601175 0.5174501181 3.2474604538M74504182 1 20

45C4066W 0,840.78

744015874501637440169

17650130

1,98

7812157800578512

D.92088

'0163

RECTIFIERS0.94/20000IL

1313

3586489 0,12MHzPrks: £4.88 each

511002E15 8.451-16148416AP.15 1007.2227,3327.9797

0:11:97.22op7,330p774F SERIES

4509845040450513

0,461,36POA

4001131 0.32400284 03240, 184 132

74180 0.94A74161 0.79

74183 1.28

741.5170741. 51731415173A

POA0 52.708c8820.52

7440682 2.6274L5683 POA7940664 3.85

,' - -64 '

74 0994

, 00TT-0 85

"9

741401190 01274HC4191 0.59744017574504192 1.20

7450174

7440191

0.650.801.38

75015790579052

988944

3.05/2908 86-ow64/7000 SIL

16,222432,40860141-5Price: E3,84 each

HM484154P-204.254Y53C256LS.80

POA

capF.100opF,22001/1

33000pF

74F00 0330007.47000774P02 8100000722/00oF

TTL Output4pin OIL Layout

450684506U6

, 4911 087 '54'1264

74164 1.16165 157

74151747440175

0.33023

7440685 POA74L8686 POA

74410573741-10573A

0 68'0.86

74504193 01274504194 1.20

74704 0.28

74700744C2407440241

0.920/2

7905757909

0.880.68

1.60

8A/288V 88-

HY53C464LS-80

POAMem 955 each

4508801361

401587 01

747741.061.37

741518274LS183

POAPOA

7.1L9697 --741.5688 1,98

744C574 0.741601195 1,2074HCT221 0.667450245

7470774F08

7440244 0921.10

79127912A

244136

1.96 Sealer/ Metal4pin Pk

HVB511000.86 8.45 47000pp 11..27Prim 18p each


Please mention ELEKTOR ELECTRONICS when contacting advertisers mMICROPROCESSOR

8 SUPPORT IC6

EF682I P 2.90EF6850P 2.30E116813097 4.66E116860968 5.35EF681321P 2.55EP610PC-35 POAH5161655 10.98H01468113AP 4.78H03-6402-9 6.16HD364469 too903-5495-9 6.889044863 POA

pcD8584P 72.22PC138584T 12.22pcF80667 8.28PCF85667 8.28pCF8570P 7.85PCF8573P 6.72PCF8574P 6.96PCF8574T 6.96p0F8591P 11.62Ii6502AP 4.82565208 4.4006522 4.40

SCM66115P 3.40SGS7P050 4.55SP14505 5.76ULAIR6029E1 6.80UL42013140086159.72XR-15683 3.60ZNA2L029J-85 3.80ZNPCM1J-BS 8.95

1017650CFD 5.88CL7650S570627CL765285708.24CL7652CPD 824CL7660CPA 1,40CA66055743.80CL76625PA 44051_7663BCJA 6.78CA766395745.10CL7664CPA 7.9501766545744.98CL7673CPA 1.38

LM343H 8.80LM3485 296LM3480P 0.40LM34135 040LM3507 6.85LM35114 2.80LM358N 0.32LM359N 4.68LM360H 7.72LM36131/srod 640LM3638-100 16.50LM3690 4 3.82

NE527N 3.71NE53211 0.60405364 4.90NE55304 3.82NE553244 1.58NE5532N 0.80NE5534AN 1.80NE5555 0.20NE556iSMD 0.70NE5565 0.36565585 2266E5645 3.42

TUNIACP 1.84TL071 CP 0.64TL072457 1.48TL0720N 0.50TL072CP 0.50TL074454 2.85TL07454 0.9811081CP 0.48TL08255/CP 0.131IL694CNICP0.84TL2742CD 1.96TL497ACN 3.44

75174NG 3.6875175 2.60751764 1.61)

751768 2.287517687 4.9875177 2.6075178 2.6075182 2.8075183 2.6075188 0.4075189 0.85'51899 0.85

.0243c 19000785 1.1280x67650396Bc,95.cBp -ggBF200 0.18BP2566 0.30ElF2560 0.3865299 0.4613F324 0.288F-421 0.12

Personal Computer Products

MOTHER BOARDVESA 486 3154slots.256k0ache E 85with ZIFF Socket Int CPU and8x32 h 2372Pin SIMM Socketsaccepts 486SX/DX/DX2-613 CPU(without CPU&DRAMI

MICROPROCESSORS804865X-33MHz INTEL £ 758048620-33MHz INTEL E 125804860X2-66MHE INTEL £160

1001140E5 7.4010014105 9.806303XP 8.766321P 42063485,aurn 19.95

n n75360358 1--6502 3.7665029

,,.,.65 P

;,0---LINEAR & MSC&

363013M/BB 3.4049520/86 POA

522

1

4905 26

4046505SP POA40468028 PDA

R6522AP 5.8006550282 6.82

555 -TIMER 0.206341-1J POA

CL80524570873CL8068AJD 1118

LM369C1R5 3.70LM38011 1.20

585658 2.94NE5678 0.65

TL5075P 4.03TL77024CP 2.04

75361 2.8475365 2.72

BF450 0.20BF451 0.22

Heat Sink 0 Fan for 485CPU L 10

HARD DISK DRIVES65515

4063218 4.20 865502P9 7.15 741-0PANIP 018 CL806915so 3.75 LIZ381AN 7.86 NE56814 POA TL77054CP 2.04 754374 3.26 13F494 0.16 270MB 13rnsec 3 5' LP £149135CO2P2 5.

90634857332 32.50 1165CO2P4 8.95 AD52021,1 POA 51.8069dosq 2.88 LM385Z-1.2 2.20 5E5705 4.60 71.7705CP 2.04 754508 0.64 BEIB9 0.26 340MB 13rnseo 15' LP 5 17965CO2P3 6.98

40636103XP 11.95H0680018 11.59

065510202 6.8506552182 5.96

A0524 21.529053424 48.27

CL80690C262.88CL8211CPA 2.56

LM3852-2.5 2.20LM38661-1 1.65

585715 3.406E5695 4.25

TL77094CP 2.04TL7770-65 3.82

75451 0.28754518 0.46

Bc9., 0.66BF920 0.95 FLOPPY DISK DRIVES

65C102P2 7.00 40684557 5.55 R65522122 4.80 A0637JH POA CL82, 2574 248 LM3865-1 1.40 NE592/0M0 1.80 TL783565 5,10 75452 0.26 66982 0.88 1 44MB 3.5' 28'

65C22P265551E-1655516.2

4.663904.38

60666528 POA1-1068B21P 3.92

SA68053212 5.95SAB80532.166141 6.98

4054828 1.8080574960 64.66

5M71701120 696M720741707.94

16366N3 1.80LM3864-4 2.60

6E5925 1.4060592914 0,92

TL5154175 16.03TLC220157 374

754526 0.4875453 0.64

BF065 1.79Spp532GH2 0.48

1.2/06 525'GRAPHIC CARDS

680007-8 6.78HI3.7159.5 20.98 0404138155-P182 AD578JN POA CM7207IPD 7.94 LM387AN 5.90 6E602NrAN 2.96 0110227455 265 754538 0.84 BFF191-5014k 0.90 ISA TRIDENT TVGA 89000 15413248

680007-10 7141HI3-71594-5 23.46HM10422 14.30

060825947 3.5948805535-N 11.67

9058124 8.92A0581//CSNerld 9.97

5M7209174 495CM7211Amipl 4.68

193885-1 4.25LM3995 3.40

6E60445 8.24NE6055 8.60

71525158 2,54TLC2652CP 4.92

75454 0.64754548 0.98

BFF1914.6GHz1 .20BPD/10 1.20

ISA TRIDENT TVGA 9000 51210 2 28VL Bits Graphic Card 1µl82 55

680007-18680008-8

18,208,50 0025864 17.06 A082554 -2-P 4,12 4058540 31.56 CM7211MIPL 4.68 LM36005 1.60 5E612461 2.57 TLC26545P 4.84 75462 0.98 13F048 046 expandable to 2Mega Bytes

68008P-8 m64024IPL 10.20 B825554-26 480 AD5925N POA 557212Arnip1445 LM390944 2.64 528821D7 12.06 TLC2715P 0.84 75463 1.10 BF4..0-99 MEMORIES (SIMM)680101,120.30616402181 7.75 C8054518816413.60 AD594A0 16.80 5M7213170 698 LM3914N 4.40 OP075.1 3.60 TLC272CP 1.30 75468 3.60 BF0.. 1Mx9x3 CHiP 70116 2 28

68007 5.701.59M64031P1 10.80 58705155F90 31.95 AD595AD 15.24 CM721641J1 29.32 LM3935 0.30 OP07CN 0.95 TL5272C0 4.10 75469 1.30 Bp089 -woe (4µ67281N) 70n5 6 1096802P 9.90 M026001,15 9.40 C67C51C0040 3195 4064825 3.40 5M7217417112,32 LM393P 0.30 opolep 0.95 TLC274CN 2.40 75470 POA gc-0.50 0.30 2566x93 CHIP 80n5 E 12

68038 7.985062505 7,80 C42651501r211 3.35 4070755 3.40 CA172176116 1298 1114394CN 5.98 0110/E8 3.10 TLC339CN 1.98 75471 1.68 86652 0.34

I/O CARDS Cables6805036 14.75

5082505-B 7.60 CN2661ccn26 3.35 4071126 2.34 5M7217IJI 1298 LM3999Z 2.76 OP110P 5.85 71.5372517 1.40 75472 1.48 Etcygg 092 withIDE 21102E02S/1P/1G E 15

68108 ,,0. M.5M82551AP 5.89M5M825547-6 6.57

06R4-1555 298L16C552FN 1268

310712J19 3.72AD724529//461 POA

CA/172184121 8.68CM721841PI 868

LM399H 7.851_144250J 11.82

OP177FP 3.71OP27GP 2.89

TLC551CP 3.68TLC555CP 0.65

75473 1.4875474 2.26

60107 0.2860170 0, SOB Mulk I °Lard 5 25

68217 1.806466031441251 4.52 MP700276-2 497 AD736JN 9.12 CM721801J1 8.68 L5155504 0.28 OP42FZ 7.44 T11555655 1.58 75477 2.10 65260 0.52 KEYBOARDS & MICE68408

6644P3.22

1MAB8035411.-61. 5.98 M7808547-2 5.98 AI/741M 3.69 5117218Eill 1476 LM5650N 7.48 0P770P 2.07 111C752455 5.24 75491 0.68 B.060 0.48 102 UK Enhanced KeyBoard £ 17

6845Pµ5101 03P 2.89 MS3205104L 988 A07523K5 9.80 5M7224IPL 11.92 LM710CH 2.80 OPO7CN 0.95 11E20610p 2.20 75919176 2.68 0.38 102 UK ligh Quality Keyboard E 25

6845SP 540 61C10115L 385 MS32OC25FNL 17 20 50753728 34.98 CM72264111 37.20 11M723CH 2.80 P5A4837-K 35.80 TLE20625P 3,40 75513192 228 80x21 0.48 KeyBoard

68400 7 POAMC10115P 2.89 MS32002506_67 47 40753714 POA CM7226Bi0l 32.52 L61723C6 0.70 PM7548HP 18.20 TLE2064C11 3.45 75ALS193J 3.22 65461 1.85 3 Button Serial Mouse E 8

66409868421P

....T'TT

M5146E105E212 8.946568000P/2 POA

MS3477NL 6.68MS3700NSB 8 78

42/7542XN 36.3541)7543JCWE POA

CM7249113M POAa/7555113A 1.20

11A1733C4 2.65Lfil 74101-14 220

65 9841365 0.

R 04193N POA1LE2161CP 242TMS3477NL 5.96

7551159 2.887501406 2.73

81136600 1.10501646 4.94IMPORTANT

68440P 2,56 170660001,16 18.20 M03702450 8.78 90757865 46.15 CM7555174 064 LM741CN 045 8041945 2.85 TPIC24O6NE 7,14 750165 3.98 BU211 1.60 All prices are excluding VAT.

68450P685098681321P 1

MC68010710 POAMC68010712 P09MS77501NLMC6802P 2.47

M53835AN5 7.5510.74

MS99004L 24.40

A0844A5 9.70A000804LCN 6,80405804LCWM12.10

057556170 1.85M64031P11 12.921272 2.74

LM747CH 2.401.4174755 0 90LA/780CP 2.40

65420755 1.92554558 0.905045568 0.80

TP152802K0 9,42TPIC62594 3.2817156273N 128

750188 1.207501894 1.3275518940 1.32

002119602479198214

Postage &Packing Charges.00 for orders upto 240 exc. V.A.T.

and68B4OP80605

2

P

µC68098 6.78M56821P 1.80

A/599011XL 14.16M5990245L 1594

405082055N 22.4040513834555 1980

L272M 2.301.293.8 3.84

LM79307 2.401A16334 2.82

8EF0107 3.33REFO I HP 3.33

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14

MINI AUDIO DACDesign by T. Giesberts

A digital -to -analogue converter is described, which isintended to be connected directly to a compact disc player ordigital cassette recorder. A special feature of the circuit is the

possibility of feeding its clock signal to the digital soundsource to prevent the conversion causing any jitter. Including

the power supply, it is contained on a printed -circuitboard that is somewhat smaller than eurocard size.

triving for perfect sound reproduction%.-.3is a way of life for many audio enthu-siasts. To that end, this magazine publisheda digital -to -analogue converter (DAC) in1992 which had several switched digitaloutputs. Although the present unit israther different to the earlier one, it stillcombines good audio properties with com-pact construction and reasonable cost.

The converter may be built into an ex-isting compact disc (CD) player, or it canbe constructed in a dedicated enclosurefor use as a stand-alone unit.

Circuit descriptionThe circuit is dominated by two ICs: interfacereceiver IC2 and D /A converter IC3.

The S/PDIF input signal is applied viaK1 to inverter IC la, which, owing to R2 andR3, operates as a analogue amplifier witha gain of 16 dB. The edges of the outputsignal of the inverter are enhanced by IC lband then applied to IC2.

Crystal X1 provides a clock of 16 MHzin the absence of an input signal. ResistorR6 and capacitor C6 constitute the timeconstant for the internal PLL-VCO (phase -locked loop voltage controlled oscillator).Network R5 -05-D1 resets the clock switch-ing section of the IC when the supply isswitched on.

The sampling frequency of the receivedsignal is indicated by D2, D3 and D4.These LEDs are controlled via outputs S1and S2 of IC2, with IC 1c and IC id func-tioning as buffers. Output DEF switcheson D6 via T1 if the signal has preempha-sis.

Diode D5 is an error indicator which iscontrolled via output ERR. Depending onthe nature and type of interference on theinput signal, this output is not alwaysactive, but often provides short pulses.Network R16 -C9 -D7 enables the circuit toreact to these pulses also: it causes the out-put of the converter to be muted for sometenths of a second when an error occurs.The error signal is buffered by ICI, beforeit is applied to the mute input of IC3.

A number of signals is applied to IC3 byIC2: the sampling rate clock, LRCIN; the

bit clock, BCKIN; the deamphasis switch-ing signal, MD and MC; and, dependingon the status of jumper JP1, the oscilla-tor clock, XTI.

The deemphasis must be set accord-ing to the three sampling frequencies: inthis description it will be assumed to be44.1 kHz. Note that preemphasis is usedonly with older CDs. This is just as well,because the internal digital deemphasisis the weak point of IC3: it shows a devi-ation of almost 1 dB with respect to thetheoretical correction characteristic.

The system clock for the converter is pro-vided by IC2 or by X2. This crystal may havea value of 2561, or 384.fs, where fs is thesampling frequency of the applied data. Thefrequency is set by a logic level applied topin 23 via jumper JP2.

If a quartz crystal is used, it must alsoserve as the system clock for the equip-ment to which the converter is connected.This means, of course, that only one pieceof equipment can be connected to theconverter, but this will normally not cre-ate a problem.

If IC3 derives its clock from IC2, viaJP1, the clock frequency is determined bythe input signal. This may create a diffi-culty, however, because the stability ofthe system clock is all-important for adelta -sigma converter. All jitter and noiseare reflected in the audio spectrum and thenoise shaping used in this type of con-

verter suppresses these spurious signalsonly partially. A quartz clock gives muchbetter performance as far as the dynamicrange and the signal-to-noise ratio in theaudio band are concerned. It is, there-fore, advisable to use a separate quartz clockfor IC3 and not use the clock derived by IC2from the received data stream.

This arrangement resembles that of aCD player and stand-alone converter. Sucha combination uses two links: one for thedigital audio data and the other for inter-connecting the system clock between thetwo units. Although this means an extralink, it is a very good way of obtaining thebest from the combination.

The additional output required when thequartz oscillator is used as the systemclock for the equipment connected to theconverter is provided by IC4 via Tri and K2.Since the frequency is 8.192-18.432 MHz,the link between the two units must be 75 C2coaxial cable.

The transformer prevents an earth loopforming. The specified core material pro-vides excellent coupling so that the theor-etical transformation ratio is achieved inpractice.

Capacitor C22 ensures that the screenof the coaxial cable remains at ground po-tential. Resistor R10 damps any oscillationsthat may arise in open -circuit conditions,while R11 limits any reflections occurringwhen the cable is not terminated correctly

Main parameters

Sampling frequency: 32 kHz, 44.1 kHz and 48 kHzStereo multi -level noise -shaping delta -sigma digital -to -analogue converterEight times digital oversampling filterIntegral digital deemphasisSystem clock may be connected to CD player or DAT recorder for minimum jitterNominal input voltage: 0.5 V into 75Nominal output voltage: 2 V r m.s. (Rioad >600 4)Frequency range: 10 Hz to 20 kHz, +0 dB, -0.5 dBSignal-to-noise ratio. >110 dB, A -weightedTHD+noise at 0 dB and 1 kHz: <0.0025% (measunng bandwidth limited to 30 kHz)Channel separation. >100 dB at 1 kHz; >75 dB at 20 kHzNon -linearity: <0.2 dB at signal levels up to -100 dB


MINI AUDIO DAC

to one.In the connected equipment, the co-

axial cable is linked to the input of the ICto which the crystal of the original systemclock was connected. It is thus necessaryto make sure that the system clock in thatequipment is similar to that in the con-

verter. The cable must be terminated bya 75 t2 resistor and connected to the IC inputvia a 1 nF capacitor. The level at this pinis about 1.5 VPP'

The analogue, third -order lowpass fil-ter in IC3 gives 0.2 dB attenuation at20 kHz, which is not sufficient, so that an

external filter has been added. This is es-pecially important when 1 -bit equipmentis used owing to the high noise level pre-sent above 20 kHz.

The filter is a fourth -order type basedon IC5, which provides the wanted slope.To ensure equality of the two channels, the

K1

S/PD1F

BAT85

R3

IC1b

Cl180 R2

BC547B

DEEMPHASIS

135

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PCM1710UESTI R

EXT2R

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1N4148

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IC1c

5E

C5

100n

* see text

C12

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0 0 0

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9110M

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32- kHz

R13

R12

D3

48- k Hz

C24 R18

P2OM

C29

2µ2

5V

013

12IC4d-1

11

8

125

820p

R19 R20

C26MEI

71n5

130

820p

R27 R28

100n

Tr1

Tr22x 9V3VA3

H1 N4002

C46O40V

I C27

560p

R37

1N4002

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R21

132560p

R29

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77n

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IC8

IC6

7808

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IC1 = 74HCU04IC4 = 74HC86IC5 = NE5532

940099 - 11

Fig. 1. Circuit diagram of the mini audio digital -to -analogue converter.


16 AUDIO & HI -Fl

uNR14cp* vfrc4k*gP12 (9

The PCM1710UThe PCM1710U from Burr -Brown is amulti -bit, fourth -order delta -sigma digi-tal -to -analogue converter (DAC). The di-agram shows the various functions pro-vided by the device. The serial interfaceaccepts 16 -bit and 20 -bit data formatsfrom most current DSPs or AES/EBUinterfaces. As an option, the 16 -bit I2S busformat may be used. To be compatible withsystems to come, the device also has a dou-ble -speed mode (in which data at twicethe current sampling rate of 44.1 kHzcan be processed).The PM1710U makes an analogue volumecontrol superfluous, because it has an in-tegral. preset logarithmic 127 -step at-tenua t or, which may be controlled by a7 -bit code (riot used in the present con-verter, since that would have meant anadditional processor). A soft -mute cir-cuit, which prevents spurious signalsentering the IC, has been added to the elec-tronic amplitude control.I3efore the digital data reach the IC, theyare passed through an FIR filter withN8 oversampling. This gives a dampingfactor of -62 dB outside the audio band.

LRCIN

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940099-13

Jere also, if needed, does deemphasis takeplace at digital level. The ripple in thepassband is 0.008 dB.The basis of the PCM1710U is a newlydeveloped multi -bit delta -sigma con-verter. The advantage of this over 1 -bitconverters is the lower oversampling fre-quency. This results in a more equal dis-tribution of noise over the audio band,which in turn gives abetter signal-to-noiseratio at higher frequencies. Moreover,the circuit is much less sensitive to clock -induced jitter. The signal-to-noise ratiois about 100 dB, and the manufactur-ers specify a dynamic range of 98 dB.Distortion+noise amount to 0.0025%.An additional stage in the IC protects itagainst externally generated jitter and in-terference.The pulse-wid h -modulated output sig-nal of the IC is reconstructed by an in-ternal passive second -order filter and anactive first -order filter. The CMOS op ampused for this delivers up to 3.2 Vppto a loadof 5 kt2.The PCM I 7 IOU, which is housed in a28 -pin SOIC case, requires a single powersupply of 5 V.

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Fig. 2. Printed -circuit board for the D/A converter (overlay on opposite page).


Fig. 3. How to construct the outputtransformer for the clock signal.

filter components need a tolerance of 1%;Table 1 gives the values for a Butterworthand a Bessel characteristic. The compo-nents specified in the parts list have avalue that gives a compromise between thesecharacteristics.

The op amps also function as ampli-fier/buffer. Their gain raises the 3.2 Vppoutput of IC3 to 2 Vr, at K3 and K4. Bufferingis needed because the op amp in IC3 must

see a load of ka The op amps draw afairly large bias current, resulting in arather large voltage drop across R17 -R21and R25 -R29, which is compensated bypresets P1 and P2.

Relay Rei , in conjunction with T2 andT3, mutes the clicks caused by on and offswitching of the supply. The supply volt-age to these transistors, which are cas-caded, is 25 V. When the supply is switchedon, it takes a few seconds (time constantR34 -R35 -C47) before T3 conducts. ResistorR36 arranges for T3 to function as a cur-rent source so that the current throughthe relay has virtually no ripple in spiteof the low value of C46.

Transistor T2 ensures that relay is de -energized rapidly when the supply isswitched off, since it will cut off as soonas its base potential, derived from voltagedivider R33 -R34, drops below 1 V. Thisvalue may be altered slightly as requiredby changing the value of R33.

The circuit uses supply voltages of ±8 Vfor the analogue section and ±5 V for thedigital section. These supplies are isolatedfrom one another up to IC3 by trans-former Tr2. Resistors R37 and R38 limit thecharging current to C51 and decouple the

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MINI AUDIO DAC 1111

supply lines for RF. The value of C51 ishigher than usual to reduce the ripple onthe supply lines to the digital section to aminimum. The supply line to IC3 is addi-tionally decoupled for RF by LI. The supplylines to IC5 are additionally decoupled forRF by L2 and L3.

ConstructionThe converter is intended to be built on theprinted -circuit board in Fig. 2. Note thata number of components must be sol-dered in place upright.

If polypropylene instead of polystyrenecapacitors are used for C25 -C28 and C30 -C33,the filter characteristic will be slightly lessaccurate. The capacitors should be matchedon a capacitance meter to ensure thattheir values in the two channels are iden-tical. Deviations between the channelsare far more disturbing than a somewhatless accurate filter characteristic. The typeof filter is an individual choice. A Besseltype has no overshoot or ringing and theimpulse response lacks oscillatory be-haviour, but its frequency response israther less selective than that of a Butter-worth type. Also, the latter has good tran-sient characteristics.

Output transformerTri is formed by lay-ing a 15 -turn primary and a 5 -turn sec-ondary winding on to a G2-3/FT12 toroidalcore as shown in Fig. 3. Windings asshown keep capacitive coupling to a min-imum. After soldering the terminals inplace, fix the transformer on the boardwith a few drops of appropriate fast -set-ting glue.

Circuit IC3 is a surface -mount device(SMD). Such a device is best fixed with a

Fig. 4. The D/A converter constructed as a stand-alone unit.


18 AUDI() & HI-FI

26 SEP 9410:11.12

drop of glue: make sure that the pins arein the correct position, and then solder thepins in place.

The answer to the question of whetherto use a dedicated crystal for the systemclock or not depends on what purpose theconverter is to serve. If it is intended to im-prove the performance of a CD player,open the case of this and note the valueof the crystal (modern players use only asingle crystal). If the frequency is11.2896 MHz or 16.9344 MHz, the clockof the converter may be used. In otherequipment, such as a DAT recorder (butnot a CD player), with a sampling fre-quency of 48 kHz, the crystal must be

AUDIO PRECISION CD.RFSP2 OIPIABrl FRF01110

2.00101

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12.228 MHz or 18.432 MHz or, if the sam-pling frequency is 32 kHz, the crystalshould be 8.192 MHz or 12.288 MHz. Ifso, the clock of the converter may be used.Remove the relevant crystal (and the twocustomary ceramic capacitors) from theCD player (or DAT recorder) and use it asX2 in the converter circuit. If the frequencyis the lower of the pair stated, set thelink of jumper JP2 between 1 and 2; if thehigher of the two, set the link between 2and 3. Also, set the link of JP1 between 2and 3.

The system clock from the converteris connected to the free pins on the rele-vant IC in the CD player (or recorder). Which

11.1010 PRECISION COCROSS1 X1,1.15010

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940099-1

(a)

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940009 1

(e)

way around is quickly seen on the circuitdiagram of the equipment. If this is notavailable, solder the link in place: if theplayer does not work, reverse the con-nections.

If the crystals frequencies are differentfrom those given, the converter clock cannot be used as the system clock. In thatcase, omit X2 and use the system clock ofIC2 by placing the link on JP1 between 1and 2. The clock output circuit based onIC4 and Tr' can also be omitted.

Solder pins in the LED positions so thatthe diodes can be fitted directly on thefront panel of the enclosure (if used) andlinked to the pins by short lengths of equip -

AUDIO PRECISION 141inear ANDPASS.,-) r, LEVE014111

2.0000

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950099 19

(f)

Fig. 5. Measurement results of prototype. (a) The frequency characteristic is virtually straight at 10 Hz, but at 20 kHz the deviationresulting from the output filter is about 0.4 dB. (b) Crosstalk between the two channels. (c) Non -linearity of the converter

becomes only ooticeable between -90 dB and -100 dB . (d), (e) and (f) are Fourier analyses of a 997 Hz output signal; at (d) theclock for the converter was derived from the digital input signal via the YM3623B; at (e) the converter had a dedicated crystal thatwas also linked to the CD player; the distortion residue of the 997 Hz signal is clearly visible (THD about 0.001%). The rising of theaudio band above 20 kHz is typical of a noise -shaping DAC. The falling off above 50 kHz is caused by the analogue output filter.

The noise in the audio band is here almost 30 dB lower than at (d). (f) shows the same situation as in (e), but without the analogueoutput filter. Note that the noise in the audio band is appreciably higher.

I

940099-F

Fig. 6. Suggested front panel for the D/A converter (not available ready made) (scale 3:4).


MINI AUDIO DAC

ButterworthAttenuation at 20 kHz (filter + DAC): about 0.3 dBR18, R20, R26, R28 = 10.7161, 1%R10, R27 = 3.65 ks2, 1%R21, R20 = 3,16 kit, 1%C25, C30 = 1 nF, 1%C26, C31= 1.5 nF, 1%C27, C32 = 560 pF, 1%C28, C33= 330 pF, 1%

BesselAttenuation at 20 kHz (filter + DAC): about 1 dBR18, R26 = 6.49 kit, 1%R19, R27 = 2.87 la 1%R20, R26 = 5.49 MI, 1%R21, R20 = 2.49 kSZ, 1%C25, C30 = 820 pF, 1%C26, C3/ = 1.5 nF, 1%C27, C32 = 560 pF, 1%C2,8, C33 = 330 pF, 1%

Table 1. Component values for different types of filter.

ment wire. The LEDs are not required if acommon system clock is used.

The board may be built into a CD playeror constructed as a stand-alone unit (seeFig. 4). If the latter, a suggested frontpanel layout is shown in Fig. 6. Make surethat the audio output sockets at the rearof the enclosure are in line with the rele-vant connections on the board. Also, sock-ets are required for the system clock (if used)and the digital audio signal. These mustbe connected to the board by short lengthsof coaxial cable. Finally, a mains entrywith integral fuse and a mains on/offswitch must be fitted

Adjusting the presetsConnect a multimeter (set to lowest di-rect voltage range) to one of the the out-puts of the converter. Switch on the mainsand let the circuit warm up for 10-15 min-utes. Do not apply an input signal andadjust the relevant preset for zero read-ing. Connect the multimeter to the otheroutput and adjust the other preset for zeroreading.

Parts list

Resistors:R1, R11 = 75lR2, R24, R32, R36 = 100 QR3 = 10 ki-2R4= 1052R5= 18 kS2R6, R10 = 270 0R7 = 1 MQR8 = 2.2 S2R9, R13 = 560 S2R12, R14 = 680 QR15 = 470 QR16 = 22 MC2R17, R25 = 47.5 kS2, 1%R18, R19, R26, R27 = 4.64R20, R28 = 7.87 kS2, 1%R21, R29 = 4.99 kS2, 1%R22, R30 = 2.55 k11, 1%

R23, R31 = 2.00 kS2,1%

R33 = 820 lic2R34 = 10 MilR35- 1.5 MQR37, R38 = 5.6 QP1, P2 = 10 MS2

preset

Capacitors:C1 = 10 nF ceramicC2, C 16-C21 , C23,C36 -C39, C42, C43,

C48, C50 = 100 nF,

AP Performance AudioThe Journal of High Performance Audio Construction

Editor ; Graham Nalty M.A. (Mechanical & Electrical Sciences - Cambridge)

- 1 - - - i -

Gain Linear Transistors - Better Specs - Better Sounds?

Avalance Soft Recovery Diodes - Lower RFI?

Plicaps - Lower Impedance, but do they sound better?

Loudspeaker Upgrading - Solen Polypropyleues at the value you want!

The Apex Power Amplifier - Designed in 1987, but still going strong!

Vishay Bulk Foil Potentiometer - The best continuous volume control?

Sonic Link Green 75 OHM - Better CD to D -A, but how about the TV reception?

The Impossible Dream - Up to 100 Watts Single Ended Class A!

Elektor Amplifier Projects - AP can supply the parts you need.

High Performance Car Audio - A challenge for Audiophiles?

Basement Bargain Bin - Which parts at Silly Prices this time? *

Plus Readers Prizewinning Letters and much more.

Issue 2 available early December - Send .£1 or 5x1 9p stamps1995 Subscription £5 (overseas £10) includes December 1994 issue

AP ElectronicsAudiophile Parts at Affordable PricesHotline For Free Technical Advice -

Tel: 01332-674929 9-10am Mondays -Sundays

1995 CATALOGUE now available - £4.95(or FREE with your next £40 + order)

VI I

Please make cheques payable to "Audivkits"

Credit Card Telephone Order Hotline 01332 674929(messages recorded when unattended - please give full details)

Derwent Business Centre, Clarke Street, Derby DE1 2BUTel: +44-1332-674929 Fax: +44-1332-298836

ceramicC3, C4 = 10 pFC5 = 100 nFC6 = 8.2 nFC7, C22 = 47 nF ceramicC8 = 4.7 pF, 63 V, radialC9 = 15 nFC10 = 47 PFC11 = 39 pFC12, C13, C34, C35, C40, C41, C49 = 10 pF,

63 V, radialC14, C15 = 100 pF, 10 V, radialC24, C29 = 2.2 pF, polypropylene,

pitch 5 mmC25, C30 = 820 pF, 1%*C26, C31 = 1.5 nF, 1%*C27, C32 = 560 pF, 1%*C28, C33 = 330 pF, 1%*C44, C45, C51 = 1000 pF. 16 V, radialC46 = 22 pF, 40 V, radialC47 = 2.2 pF, 63 V, radial*polystyrene (preferred) or polypropylene

Inductors:L1 -L3 = 47 pH

Semiconductors:D1, D11 = 1N4148D2, D6 = LED, yellow, low currentD3, D5 = LED, red, low current

1% D4 = LED, green, low currentD7 = BAT85D8 -D10 = 1N4002B1 = B80C1500 rectifier bridge

Tl = BC547BT2 = BC516T3 = BC517

Integrated circuits:ICI = 74HCU04IC2 = YM3623B (Yamaha)IC3 = PCM1710U (Burr -Brown)IC4 = 74HC86IC5 = NE5532IC6 = 7808IC7 = 7908IC8 = 7805

Miscellaneous:JP', JP2 = 3 -way PCB header with linkK1 -K4= audio socket (chassis mounting)K5 = 2 -way terminal block, pitch 7.5 mmCore for Tr' = G2-3/FT12Enamelled copper wire 0.7 mm dia. (for

winding Tr') as requiredTr2 = mains transformer, 2x9 V, 3.3 AX1 = crystal, 16 MHzX2 = crystal 11.2896 MHz or 16.9344 MHzRef = relay with 2 change -over contacts,

coil 12 V, 10 mAEnclosure, ESM ET24/04, 180 mm deep

(Maplin)PCB Order No. 940099-1

1940099]



PC PAL VGA TO TV CONVERTER Converts a colour TV intoa basic VGA screen. Complete with built in psu, lead and sAvare£49.95. Ideal for laptops or a cheap upgrade.EMERGENCY LIGHTING UNIT Complete unit with 2 doublebulb floodlights. built in Charger and auto switch. Fully cased. 6v 8AHlead acid req'd, (secondhand) £4 ref MAG4P11.GUIDED MISSILE WIRE. 4200 metre reel of ultra thin 4 coreinsulated cable, 28lbs breaking strain, less than 1mm thick! Idealalarms, intercoms, fishing, dolls house's etc. £14.99 ref MAG15P5SINCLAIR C6 13" WHEELS Complete with centre bearing(cyde type), tyre and inner tube. £6 ea ref MAG 6P10. Ideal go kart300v PANEL METER70X60X5OMM,AC, 90 degree scale. Goodquality meter. £5.99 ref MAG 6P14. Ideal for monitonng mains etc.ASTEC SWITCHED MODE PSU BM41012 Gives +5a 3.75A,+1201.5A, [email protected]. 230/110, cased, BM41012 £5.99 ref AUG6P3.TORRODIAL TX 30-0-30 480VA, Perfect for Mosfet amplifiersetc. 120mm dia 55mm thick. £18.99 ref APR19.AUTO SU NCHARGER 155x300mm solar panel with diode and3 metre lead fitted with a agar plug. 12v 2watt. 0.99 ea ref AUGTOP3.FLOPPY DISCS DSDD Top quality 5.25" discs, these have beenwritten to once and are unused Pack of 20 is £4 ref AUG4P1.MOD WIRE Perfect for repairing PCB's, wire wrap etc. Thininsulated wire on 500m reels, Our price just E9.99 ref APR10P8.12v MOVING LIGHTCorarouer. Madeby Hella, 6 channels ratedat 90watts each. Speed contrd, cased. £34.99 ref APR35.ECLATRON FLASH TUBE As used in police carfiashing lightsetc. full spec supplied. 60-100 flashes a min. £9.99 ref APR10P5.24v AC 96WATT Cased power supply. New. £13.99 ref APR14.MILITARY SPEC GEIGER COUNTERS Unused and straightfrom Her majesty's forces. £50 ref MAG 50P3.STETHOSCOPE Fully functioning stethoscope, ideal for listeni ngto hearts, pipes, motors etc. £6 ref MAR6P6.OUTDOOR SOLAR PATH LIGHT Captures sunlight duringthe day and automatically switches on a built in lamp at dusk.Complete with scales lead add battery etc £19.99 ref MAR20P1.ALARM VERSION Of above unit comeswith built in alarm and pi rto deter intruders. Good value at just £2499 ref MAR25P4.CLOCKMAKER KIT Hours of fun making your own clock, com-plete instructions and everything you need. £7.99 ref MARSP2.CARETAKER VOLUM ET RIC Alamo, will cover the whole of theground floor against forcred entry. Includes mains power supply andintegral battery backup. Powerful internal sounder, will take extemalbell if req'd. Retail £150+, ours? £49.99 ref MAR50P1.TELEPHONE CABLE White 6 core 100m reel complete with apack of 100 dips. Ideal 'phone extns etc. £7.99 ref MAR8P3.IBM PC CASE AND PSU ideal base for building your own PC.Ex equipment but OK £9.99 each REF: JUN10P2.MICRODRIVE STRIPPER Small cased tape drives ideal forstripping, lots of useful goodies including a smart case, and lots ofcomponents. £2 each ref JUN2P3.SOLAR POWER LAB SPECIAL You get TWO 6'x6' 6Y 130mAsolar cells.4 LED's, wire, buzzer, switch plus 1 relay ormotot.Supernvalue kit just £5.99 REF. MAG6P8SOLID STATE RELAYS Will switch 25A mains. Input a 5-26vDC 57x43x21mm with terminal screws £3.99 REF MAG4P10300 DPI A4 DTP MONITOR Brand new but shop soiled so hencebargain phoefTTLJECL inputs, 15' landscape, 1200x1664 pixelcomplete with circuit diag to help you interface with your projects.JUST £1499 REF JUN15P2.MULTICORE CABLE 300 metre red of grey 8 core cable idealfor 'phones. intercomms, computers, alarms etc. Comes inspedaldispensing container to avoid tangles. £15 ref AUG15.BUGGING TAPE RECORDER Small voice activated recorder,usesmicro cassette cornpletewith headp hones £28.99 ref MAR29P1

U LT RAM IN I BUG M IC 6mmx3.5mm made by AKG..5- 12v electretcondenser. Cost E12 ea, Our? four for £9.99 REF MAG10P2,RGB/CGAJEGAITTL COLOUR MONITORS 12' in goodcondition Back anodised metal case, £79 each REF JUN79GX4000 GAMES MACHINES returns so ok for spares or repair£9 each (no games) REF MAG9P1C64 COMPUTERS Returns, so ok for spares etc E9 ref MAG9P2FUSELAGE LIGHTS 3 foot by 4' panel 1/8' thick with 3 panelsthat glow green when a vdtage is applied. Good for night lig hts,frontpanels. signs, disco etc. 50-100v per strip. £25 ref MAG25P2ANSWER PHONES Returns with 2 faults. we give youthebitsfor1 fault, you have to find the other yourself, BT Response 200's £18ea REF MAG18P1. PSU £5 ref MAG5P12.SWITCHED MODE PSU ex equip, 60w +5v @5A. -5vQ.5A.+12ve2A,[email protected] 120/220v cased 245x88x55mm IECinputsocket £6.99 REF MAG7P1PLUG IN PSU 9V 200mA DC £2.99 each REF MAG3P9PLUG IN ACORN PSU 19v AC 14w , £2.99 REF MAG3P10POWER SUPPLY fully cased with mains and o/p leads 17v DC900mA output Bargain price £599 ref MAG6P9ACORN ARCH IM EDES PSU +5v 44A, on/oft sw uncased,selectable mains input, 145x 100x45mm £7 REF MAG7P2GEIGER COUNTER KIT Low cost professional twin tube, com-plete with PCB and components. Now only £19 REF AUG19.9v DC POWER SUPPLY Standard plug in type 150ma 9s, DCwith lead and DC power plug. price for two is £2.99 ref AUG3P4.AA NICAD PACK encapsulated pack of 8 AA nicad batteries(tagged) ex equip, 55x32x32mm. £3 a pack. REF MAG3P 1113.8V 1.9A psu cased with leads. Just £9.99 REF MAGIOP3360K 6.26 brand new half height floppy drives IBMcompatibleindustry standard. Just £6.99 REF MAG7P3PPC MODEM CARDS. These are high spec plug in cards madefor the Amstrad laptop computers. 2400 baud dial up unit completewith leads. Clearance pnce is E5 REF: MAG5PIINFRA RED REMOTE CONTROLLERS Originally made forhi spec satellite equipment but perfect for all sorts of remote controlprojects. Our clearance price is just E2 REF: MAG2TOWERS INTERNATIONALTRANSISTORGUIDE. Averyuseful book for finding equivalent transistors. leadouts, specs etc.£20 REF: MAG20P1SINCLAIR C6 MOTORS We have a few left without gearboxes.

NEW BULL ELECTRONICS STORE IN

WOLVERHAMPTON55A WORCESTER ST TEL 0902 22039

Spec is12v DC 3,300rpm £25 ref MAG25.

NEW PRODUCT200 WATT INVERTER Converts 10-15v DC intoeither 110v or 240v AC. Fully cased115x36x 156m m, complete with heavy duty powerlead, cigar plug, AC outlet socket -Auto overloadshutdown, auto short circuit shut down, auto inputover voltage shutdown, auto input under voltageshutdown (with audible alarm), auto temp control,unitshutsdown if overheated and soundsaudiblealarm. Fused reversed polarity protected. outputfrequency within 2%, voltage within 10%. A ex-tremely well built unit at a very advantageouspricellorice is £64.99 ref AUG65.

UNIVERSAL SPEED CONTROLLER KIT Designed by us forthe C5 motorbut ok forany 12v motor up to 30A. Complete with PCBetc. A heat sink may be required. E17.00 REF: MAG17MAINSCABLE Precut black 2 core 2 metre lengths ideal forrepairs, projects etc. 50 metres for £1.99 ret AUG2P7.

COMPUTER COMMUNICATIONS PACK Kit contains 100mof 6 core cable, 100 cable dips, 2 line drivers with RS232 interfacesand all connectors etc. Ideal low cost method of communicatingbetween PC'sovera long distance. Complete kit £15.99 Ref MAR16P2.

MINICYCLOPS PIR52x62x4Omm runs on PP3 battery completewith shrill sounder. Cheap protection at only £5.99 ref MAR6P4.ELECTRIC MOTOR KIT Comprehensive educational kit in-cludes all you need to build an electric motor. £9.99 ref MAR10P4.VIDEO SENDER UNIT. Transmits both audio and video signalsfrom either a video camera, video recorder, TV or Computer etc toany standard TV set in a 100' range! (tune TVto a spare channel) 12vDC op. Price is£15 REF: MAG15 12v psu is E5 extra REF: MAG5P2FNI CORDLESS MICROPHONE Small hand held unit with a500' range! 2 transmit power levels. Reqs PP3 9v battery. Tuneableto any FM receiver. Price is £15 REF: MAG15P1LOW COST WALKIE TALKIES Pair of battery operated unitswith a range of about 200'. Ideal for garden use or as an educationaltoy. Price is £.8 a pair REF: MAG 8P1 2 x PP3 req'd.*MINATURE RADIO TRANSCEIVERS A pair of walide talkieswith a range of up to 2 kilometres in open country. Units measure22x52x155mm. Complete with cases and earpieces. 2xPP3 req'd.£30,00 pair REF: MAG30COMPOSITE VIDEO KIT. Converts composite video into sepa-rate H sync, V sync, and video. 12v DC. £8.00 REF: MAG8P2.LQ3600 PRINTER ASSEMBLIES Made by Amstrad they areentire mechanical printer assemblies induding printhead, steppermotors etc etc Intact everything bar the case and electronics, a goodstripper! £5 REF: MAG5P3 or 2 for £8 REF: MAG8P3SPEAKER WIRE Brown 2 core 100 foot hank £2 REF: MAG2P1LED PACK 01 100 standard red 5m leds E5 REF MAG5P4UNIVERSAL PC POWER SUPPLY complete with flyleads,switch, fan etc. Two types available 150w at £15 REF:MAG15P2(23x23x23mm) and 200w at £20 REF: MAG20P3 (23)(23x23rnm)*FM TRANSMITTER housed in a standard working 13A adapter!!the bug runs direct}, off the mains so lasts foreverl why pay £700? orpace is £26 REF: MAG26 Transmits to any FM radio.'FM BUG KIT New design with PCB embedded coil for extrastability. Works to any FM radio. 9v battery req'd. £5 REF: MAG5P5*FM BUG BUILTANO TESTED superior design to kit. Suppliedto detective agendes. 9,, battery req'd. E14 REF. MAG14TALKING COINI3OX STRIPPER originatiymade to retail at£79each, these units are designed to convert and ordinary phone into apayphone. The units have the locks missing and sometimes brokenhinges. However they can be adapted for their original use or used forsomething else?? Price is just £3 REF: MAG3P1100 WATT MOSFET PAIR Same spec as 2SK343 and 2SJ413(8A,140v,100w) 1 N channel, 1 P channel, £3 a pair REF: MAG3P2TOP QUALITY SPEAKERS Made for HI Fl televisionsthese are10 watt 4R Jap made 4' round with large shielded magnets Goodquality. £2 each REF: MAG2P4 or 4 for £6 REF: MAG6P2TWEETERS 2' diameter good quality tweeter 140R (ok with theabove speaker) 2 for £2 REF: MAG2P5 or 4 for £3 REF: MAG3P4AT KEYBOARDS Made by Apricot these quality keyboards needjust a small modtorun on any AT,they work perfectly but you will haveto put up with 1 or 2 foreign keycaps! Price £6 REF: MAG6P3PC CASES Again mixeditypessoyou take a chance next one off thepile £12 REF:MAG12 or two the same for £20 REF: MAG20P4HEADPHONESExVirgin Atlantic 8 pairsfor£2 REF: MAG2P8PROXIMITY SENSORS These are small PCB's with what looklike a source and sensor LED on one end and lots of components onthe rest of the PCB. Complete with fly leads. Pack of 563 REF: MAG:3P5 or 20 for £8 REF: MAGBP4

'SOME OF OUR PRODUCTS MAY BE UNLICENSABLE IN THE UK

BULL ELECTRICAL250 PORTLAND ROAD HOVE SUSSEX

BN3 5QTMAIL ORDER TERMS: CASH PO OR CHEQUEWITH ORDER PLUS £3.00 POST PLUS VAT.

PLEASE ALLOW 7 -10 DAYS FOR DELIVERYinTELEPHONE ORDERS WELCOME -

TEL: 0273 203500 WMFAX: 0273 323077 -- -

SNOOPERS EAR? Original made to clip over the earpiece oftelephone to amplify the sound -it also works quite well on the cablerunning along the wall! Price is E5 REF: MAG5P7DOS PACKS Microsoft version 3.3 or higher complete with allmanuals or price just £5 REF: MAG5P8 Worth it just for the verycomprehensive manual! 5.25' only.DOS PACK Microsoft version 5 Original software but no manualshence only £3 REF: MAG3P6 5.25* only,P IR DETECTOR Made by famous UK alarm manufacturer theseare hi spec, long range Internal units. 12v operation. Slight marks oncase and unboxed (although brand new) £8 REF: MAGSPSWINDUP SOLAR POWERED RADIO AM/FM radio completewith hand charger and solar panel! £14 REF: MAG14P1MOBILECARPHONEE6.99 Well almost! complete in earphoneexcluding the box of electronics normally hidden under seat. Can bemade to illuminate with 12v also has built in light sensor so displayonly illuminates when dark. Totally convincing! REF: MAG6P6ALARM BEACONS Zenon strobe made to mount on an externalbell box but could be used for caravans etc. 12v operation. Justconnect up and it flashes regularly) E5 REF: MAG5P11FIRE ALARM CONTROL PANEL High quality metal casedalarm panel 350x165x80mm.With key. Comes with electronics butno information. sale price 7.99 REF: MAG8P6REMOTE CONTROL PCB These are receiverboards for garagedoor opening systems. Another use? E4 ea REF MAG4P56"X12" AMORPHOUS SOLAR PANEL 12v 155x310mm130mA. Bargain price just £5.99 ea REF MAG6P12.FIBRE OPTIC CABLE BUMPER PACK 10 metres for £499ref MAG5P 13 ideal for expenmenters! 30 m for £12.99 ref MAG13P 1LOPTX Line outputtransformers believed to be for IBM hi rescolourmonitors but useful for getting high voltages from low ones! £2 eachREF: MAG2P12 bumper pack of 10 for £12 REF: MAG12P3H EATS1NKS (finned) 10220, designed to mount vertically on a pcb50x40x25mm you can have a pack of 4 for £1 ref JUN1P11.WATERPROOF JUNCTION BOX 65rnm dia 33mm deep. Fourcable entry exit pd nts (adjustable for any size cable) snap fit lid. Idealfor TV, satellite use. £2 ea ref APR2 or 6 for £10 ref AP R10P7.

BOTH SHOPS OPEN 9-5.30SIX DAYS A WEEK

INFRARED LASER NIGHT SCOPESSecond generation image intensifiercomplete with hand grip attachmentwith built in adjustable laser lamp forzero light conditions. Supplied withPentax 42mm camera mount andnormal eye piece. 1.6kg, uses1xPP3,3xAA's (all supplied )245+VatNEW HIGH POWER LASERS15mW, Helium neon, 3 switchablewave lengths .63um,1.15um,3,39um(2 of them are infrared) 500:1 polarizerbuilt in so good for holography. Sup-plied complete with mains powersupply.790x65mm. Use with EX-TREME CAUTION AND UNDERQUALIFIED GUIDANCE. L349+Vat.£01£££WE BUY SURPLUS STOCKflif.£££

TURN YOUR SURPLUS STOCK INTO CASH.IMMEDIATE SETTLEMENT. WE WILL ALSO QUOTE FOR

COMPLETE FACTORY CLEARANCE

1994 CATALOGUE.MINIMUM GOODS ORE ER EISno r )F F'. r NNMEN7 SD 1003 S,UMVERSITiES.d IOC %. E . E E . ..35SUPPL IRDSUBJECT TOOUR CONDIT IONS Of SALE AND UNLESS OTHERWISE soar CO otin RANTS ED FOR 30DAVS IE HREG ,NG0 URiCES & SPECIFICATIONS WITHOUT PR iRNOTICE ORDERS GI3RA, ' ,TT4-ITI15 W LOPEGl . .1,2R OU 03.

3FT X 1FT 1 OWATT SOLAR PANELS14.5v/700mA

£33.95inns 5200 SPECIAL PACKAGING CHARGE)

TOP QUALITY AMORPHOUS SILICON CELLS HAVE ALMOST ATIMELESS LIFESPAN WITH AN INFINITE NUMBER OF POSSIBLE AP-PLICATIONS, SOME OF WHICH MAY BE CAR BATTERY CHARG-ING, FOR USE ON BOATS OR CARAVANS, OR ANYWHERE APORTABLE 12V SUPPLY IS REQUIRED. REF: MAG34

PORTABLE RADIATION DETECTOR

£49.99A Hand held personal Gamma and X Ray detec-tor. This unit contains two Geiger Tubes, has a 4digit LCD display with a Piezo speaker, giving anaudio visual indication. The unit detects highenergy electromagnetic quanta with an energyfrom 30K eV to over 1.2M eV and a measuringrange of 5-9999 UR/h or 10-99990 Nr/h. Suppliedcomplete with handbook.Ref MAG50.



POWER AMPLIFIER MODULES -TURNTABLES -DIMMERS -LOUDSPEAKERS -19 INCH STE M LI

OMP MOS-FET POWER AMPLIFIERSHIGH POWER, TWO CHANNEL 19 INCH RACK

THOUSANDS PURCHASEDBY PROFESSIONAL USERS

THE RENOWNED MXF SERIES OF POWER AMPLIFIERSFOUR MODELS:- MXF200 (100W + 100W) MXF400 (200W + 200W)

MXF600 (300W + 300W) MXF900 (450W + 450W)ALL POWER RATINGS R.M.S. INTO 4 OHMS, BOTH CHANNELS DRIVEN

FEATURES: *Independent power supplies with two toroidal transformers * Twin L.E.D. Vu meters *Level controls * Illuminated on/off switch * XLR connectors * Standard 775mV inputs * Open and short circuitproof * Latest Mos-Fets for stress free power delivery into virtually any load * High slew rate * Very lowdistortion * Aluminium cases * MXF600 & MXF900 fan cooled with D.C. loudspeaker and thermal protection.

USED THE WORLD OVER IN CLUBS, PUBS, CINEMAS, DISCOS ETC

SIZES:- MXF200 W19"x143',x" (2U)x1:111"MXF400 W19"x315',*" (3U)*D12"MXF600W19"xH5',.," (3U)*D13"MXF900 W19"xH5',." (3U)x1314**"

PRICES:- MXF200 £175.00 MXF400 £233 85MXF600 £329.00 MXF900 £449 15SPECIALIST CARRIER DEL. £12.50 EACH

,I 0 .1

Advanced 3 -Way Stereo Active Cross -Over, housed in a 19" x 1U case. Each channel has three level controls:bass, mid & top. The removable front fascia allows access to the programmable DIL switches to adjust thecross -over frequency: Bass -Mid 250/500/800Hz, Mid -Top 1.8/3/5KHz, all at 24dB per octave. Bass invert switcheson each bass channel. Nominal 775mV input/output. Fully compatible with OMP rack amplifier and modules.

Price £117.44 + £5.00 P&P

II V N

SERVICE LARGE (A41 S.A.E., SOp STAMPED FOR CATALOGUE *

111M;2171/111A4C16171:7,151011J1:11Jail.111114.1 SUPPLIED READY BUILT AND TESTED.

These modules now enjoy a world-wide reputation tor quality, reliability and .pertormance at a realistic price. Fourmodels are available to suit the needs of the professional and hobby market i.e. Industry, Leisure, Instrumental and Hi-Fietc. When comparing prices, NOTE that all models include toroidal power supply, integral heat sink, glass fibre P.C.B. anddrive circuits to power a compatible Vu meter. All models are open and short circuit proof.

THOUSANDS OF MODULES PURCHASED BY PROFESSIONAL USERSOMP/MF 100 Mos-Fet Output power 110 wattsR.M.S. into 4 ohms, frequency response 1Hz - 100KHz-3dB, Damping Factor >300, Slew Rate 45V/uS,T.H.D. typical 0.002%, Input Sensitivity 500mV, S.N.R.-110 dB. Size 300 x 123 x 60mm.PRICE £40.85 - £3.50 P&P

= * ECHO & SOUND EFFECTS*STEREO DISCO MIXER with 2 x 7 bandL & R graphic equalisers with bar graphLED Vu meters. MANY OUTSTANDINGFEATURES:- including Echo with repeat &speed control, DJ Mic with talk -overswitch, 6 Channels with individual fadersplus cross fade, Cue Headphone Monitor. 8Sound Effects. Useful combination of thefollowing inputs:- 3 turntables (mag), 3mics, 5 Line for CD, Tape, Video etc.

Price £144.99 +- £5.00 P&P SIZE: 482 x 240 x 120mm

OMP/MF 200 Mos-Fet Output power 200 wattsR.M.S. into 4 ohms, frequency response 1Hz - 100KHz-3dB, Damping Factor > 300, Slew Rate 50V/uS,T.H.D. typical 0.001%, Input Sensitivity 500mV, S.N.R.-110 dB. Size 300 x 155 x 100mm.PRICE £64.35 + £4.00 P&P

OMP/MF 300 Mos-Fet Output power 300 wattsR.M.S. into 4 ohms, frequency response 1Hz - 100KHz-3dB Damping Factor 300, Slew Rate 60V/uS,r 'T.H.D. typical 0.001%, Input Sensitivity 500mV, S.N.R.-110 dB. Size 330 x 175 x 100mm.

I' PRICE £81.75 + £5.00 P&P

OMP/MF 450 Mos-Fet Output power 450 wattsR.M.S. into 4 ohms, frequency response 1Hz - 100KHz-3dB, Damping Factor >300, Slew Rate 75V/uS,

151, T.H.D. typical 0.001%, Input Sensitivity 500mV, S.N.R.-110 dB, Fan Cooled, D.C. Loudspeaker Protection, 2Second Anti -Thump Delay. Size 385 x 210 x 105mm.PRICE £132.85 I- £5.00 P&P

OMP/MF 1000 Mos-Fet Output power 1000 wattsR.M.S. into 2 ohms, 725 watts R.M.S. into 4 ohms,frequency response 1Hz - 100KHz -3dB, DampingFactor > 300, Slew Rate 75V/uS, T.H.D. typical0.002%, Input Sensitivity 500mV, S.N.R. -110 dB, FanCooled, D.C. Loudspeaker Protection, 2 SecondAnti -Thump Delay. Size 422 x 300 x 125mm.PRICE £259.00 + £12.00 P&P

NOTE MOS-FET MODULES ARE AVAILABLE IN TWO VERSIONS:STANDARD -INPUT SENS 500mV, BAND WIDTH 100KHz.PEC (PROFESSIONAL EQUIPMENT COMPATIBLE) - INPUT SENS775mV, BAND WIDTH 50KHz. ORDER STANDARD OR PEC.

*

Join the Piezo revolution! The low dynamic mass (no voice coil) of a Piezo tweeter produces an improvedtransient response with a lower distortion level than ordinary dynamic tweeters. As a crossover is not requiredthese units can be added to existing speaker systems of up to 100 watts (more if two are put in series. FREEEXPLANATORY LEAFLETS ARE SUPPLIED WITH EACH TWEETER.

TYPE 'A' (KSN1036A) 3" round with protective wire mesh. Ideal forbookshelf and medium sized Hi-Fi apeakers. Price £4.90 - 50p P&P.TYPE 'B' (KSN1005A) 3Y," super horn for general purpose speakers,disco and P.A. systems etc. Price £5.99 - 50p P&P.TYPE 'C' (KSN1016A) 2"x5" wide dispersion horn for quality Hi-Fi sys-tems and quality discos etc. Price £6.99 50p P&P.TYPE 'D' (KSN1025A) 2"x6" wide dispersion horn. Upper frequencyresponse retained extending down to mid -range (2KHz). Suitable for highquality Hi-Fi systems and quality discos. Price £9.99 T 50p P&P.TYPE 'E' (KSN1038A) 30," horn tweeter with attractive silver finish trim.Suitable for Hi -Fl monitor systems etc. Price £5.99 - 50p P&P.LEVEL CONTROL Combines, on a recessed mounting plate, level controland cabinet input jack socket. 85x85mm. Price £4.10 + 50p P&P.

TY

TYPE 'C'

TYPE D

A new range of quality loudspeakers designed to take advantage of the latestspeaker technology and enclosure designs. Both models utilize studio quality12" cast alurninlurn loudspeakers with factory fitted grilles, wide dispersionconstant directivity horns. extruded aluminium corner protection and steelball corners. complimented with heavy duty black covering. The enclosuresare fitted as standard with top hats for optional loudspeaker stands.

POWER RATINGS QUOTED IN WATTS RMS FOR EACH CABINETFREQUENCY RESPONSE FULL RANGE 45Hz - 20KHz

ibl FC 12-100WATTS (100dB) PRICE £159.00 PER PAIRfbl FC 12-200WATTS (100dB) PRICE £175.00 PER PAIR

SPECIALIST CARRIER DEL. £12.50 PER PAIR

OPTIONAL STANDS PRICE PER PAIR £49.00Delivery £6.00 per pair

PRICES- 150W C49 99 250W 099 99400W £109 95 P&P £2 00 EACH

THREE SUPERB HIGH POWERCAR STEREO BOOSTER AMPLIFIERS150 WATTS (75 75) Stereo, 150WBridged Mono250 WATTS (125 125) Stereo, 250WBridged Mono400 WATTS (200 - 200) Stereo, 400WBridged MonoALL POWERS INTO 4 OHMSFeatures:* Stereo, bridgable mono * Choice ofhigh & low level inputs * L & R levelcontrols * Remote on -off * Speaker &thermal Protection.

POSTAL CHARGES PER ORDER E100 MINIMUM OFFICIALORDERS FROM SCHOOLS, COLLEGES, GOVT BODIES, PLCs ETCPRICES INCLUSIVE OF VAT SALES COUNTER VISA AND VISA

ACCESS ACCEPTED BY POST, PHONE OR FAX

LOUDSPEAKER LARGE SELECTION OF SPECIALIST LOUDSPEAKERSAVAILABLE, INCLUDING CABINET FITTINGS, SPEAKERGRILLES, CROSS-OVERS AND HIGH POWER, HIGHFREQUENCY BULLETS AND HORNS, LARGE (A4) S.A.E.(60p STAMPED) FOR COMPLETE LIST.

McKenzie and Fane Loudspeakers are also available.

1i I I k a LI k

ALL EMINENCE UNITS 8 OHMS IMPEDANCE8" 100 WATT R.M.S. ME8-100 GEN. PURPOSE, LEAD GUITAR, EXCELLENT MID, DISCO.RES. FREQ. 72Hz, FREO. RESP. TO 4KHz, SENS 97dB. PRICE C32.71 + C2.00 P&P10" 100 WATT R.M.S. ME10-100 GUITAR, VOCAL, KEYBOARD, DISCO, EXCELLENT MID.RES. FREQ. 71Hz, FREQ. RESP. TO 7KHz, SENS97dB. PRICE C33.74 ' C2.50 P&P10" 200 WATT R.M.S. ME10-200 GUITAR, KEYB'D, DISCO, VOCAL, EXCELLENT HIGH POWER MID.RES. FREO. 65Hz, FREQ. RESP. TO 3.5KHz, SENS 99dB. PRICE 043.47 - £2.50 P&P12" 100 WATT R.M.S. ME12-100LE GEN. PURPOSE, LEAD GUITAR, DISCO, STAGE MONITOR.RES.FREO. 49Hz, FREQ. RESP. TO 6KHz, SENS 100dB. PRICE £35.64 + C3.50 P&P12" 100 WATT R.M.S. ME12-IOOLT (TWIN CONE) WIDE RESPONSE, P.A., VOCAL, STAGEMONITOR. RES. FREQ 42Hz, FREQ. RESP. TO 10KHz, SENS 98dB. PRICE C36.67 103.50 P&P12" 200 WATT R.M.S. ME12-200 GEN. PURPOSE, GUITAR, DISCO, VOCAL, EXCELLENT MID.RES. FREQ. 58Hz, FREQ. RESP. TO 6KHz, SENS 98dB. PRICE 046.71 + C3.50 P&P12" 300 WATT R.M.S ME12-300GP HIGH POWER BASS, LEAD GUITAR, KEYBOARD, DISCO ETC.RES. FREQ. 47Hz, FREQ. RESP. TO 5KHz, SENS 103dB. PRICE £70.19 - £3.50 P&P15" 200 WATT R.M.S. ME15-200 GEN. PURPOSE BASS, INCLUDING BASS GUITAR.RES. FREQ. 46Hz, FREO. RESP. TO 5KHz, SENS 99dB. PRICE C50.72 £4.00 P&P15" 300 WATT R.M.S. ME15-300 HIGH POWER BASS, INCLUDING BASS GUITAR.RES. FREQ. 39Hz, FREQ. RESP. TO 3KHz, SENS 103dB. PRICE £73.34 1 04.00 P&P

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DEBUGGING 8031/8051MICROCONTROLLER SYSTEMS

Getting a microcontroller system to function properly is no mean task, not evenfor the truly initiated. Such systems typically look dead as a doornail even if theslightest malfunction exists. The hardware and software described in this articleenables recalcitrant 8051/8031 based systems to be scrutinized in great detail

using only a PC and a simple test adaptor.

Hardware and software by Dr. M. Ohsmann

THE measurement adaptor pro-posed here will cost you not more

than a fiver for the hardware. Togetherwith the Analystor' (for 'analyser/stor-age') software distributed via theElektor Electronics Readers Services,the adaptor functions as a kind of dig-ital oscilloscope or logic analyser, andis suitable for many purposes.

The test system allows many signalsand their relations to be examined inthat crucial phase immediately afterthe reset pulse. The concept is alsouseful for testing other clock con-trolled systems. Bus contention andother problems can be analysed withthe aid of timing diagrams written bythe test program in the form of files.These files are useful for study, refer-ence and analysis.

In nearly all cases, a microcontrollersystem comprises a CPU (central pro-cessing unit) and a program memoryin the form of EPROM. If, for instance,the 80C32/8051 single -board com-puter described in Ref. 1 is built andfitted with an EMON51 EPROM(Ref. 2), it is safe to assume that thehardware design and the software areall right. However, if nothing workswhen the system is switched on, manyusers find themselves hopelessly lostfor assistance. An even more complexsituation arises if you do not know ifthe program in EPROM is correct, or ifthe hardware is an experimental de-sign which is being powered up for thefirst time. Very few designs work firsttime!

Many of you will be able to avowthat the strangest things happen with-out any apparent logic, as long asthere is a single connection error orbus short-circuit anywhere in a micro -controller system. In such cases, oneis often desperate for reassurance thatthe processor properly executes thefirst few instructions after a reset.That, unfortunately, is not as simple

as it looks. The reset pulse is oftenpretty long, (several hundred millisec-onds), and is a bit difficult to time ac-curately when generated by an RCnetwork. Once the processor starts,things appear to happen at lightningspeed: an 8051 running at a 12 -MHzclock, for instance, executes at leastfive instructions in the first 10 ps afterthe reset. To be able to examine whatis going on at such high speeds re-quires either very expensive test equip-ment, or a bright idea. The mainproblem is, obviously, the speed. So,why not reduce the clock speed, and

make a 'slow motion' recording of whatis going on in the system? The PC canbe exploited for this purpose, i.e, it canbe used to generate the slow clock aswell as the reset signal for the micro -controller system under test. After thereset, the processor is clocked soslowly that it becomes possible for thePC to read and display a set of essen-tial signals. In fact, the software sup-plied for this project displays up to17 signals on the computer screen, al-lowing you to monitor, for instance, alldatabus or address bus activity. Thetiming diagram is triggered appropri-ately by the PC itself, so that all mem-ory read/write operations becomevisible. In short, the PC stretches thetime scale during which otherwise al-most elusive signals occur.

Using a very slow clock requires theprocessor to have a so-called staticstructure. Actually, the inspiration todevelop the present debugging systemcame from the news that a static ver-sion of the 8051, the AT89C51 fromAtmel, is now available. Apart frombeing capable of fully static operation(i.e., clock speed actually down to0 Hz) this new processor, another de-rivative of the 'generic' 8051, alsoboasts four EEPROM memories.Actually, the above concept functionsproperly only with the AT89C51, be-cause a normal 8051 has a minimumclock frequency of about 3.5 MHz. Inpractice, however, a large number ofprocessors do allow quasi -static opera-tion, although that is not specified bythe manufacturer. Among the MCS-51derivates successfully used in this re-spect are:

Atmel AT89C51 (fully static)AMD P80C31BHMHS P -80C32Signetics SC87C51CCN40Philips 80051BH-3Siemens 800535


DEBUGGING 8031/8051 MICROCONTROLLER SYSTEMS EMI

Obviously, the concept proposed herecan be transferred to other processortypes, or, indeed, any other logic sys-tem capable of static operation, ofwhich the behaviour during the firstfew hundred microseconds after thereset pulse is to be examined for thepurpose of fault-finding. Interestingly,the software for the test adaptor iswritten in Turbo -Pascal 5.0, and therelevant source files are supplied ondisk along with the executable pro-gram. Modifications to meet individualrequirements are, therefore, relativelysimple to make.

The measurement adaptorThe measurement adaptor, whose cir-cuit diagram is given in Fig. 1, is con-nected to the PC via the RS232interface. As already mentioned, thePC generates the reset and clock sig-nals for the system under examina-tion. This is achieved by using the RTSand DTS handshake lines available onthe PC's RS232 port. Two more hand-shake lines, DSR and CTS, are used toread signals from the system into thePC. The conversion to TTL level is ac-complished by the cheap and generallyavailable MAX232 integrated circuit.Next comes a 74HCT541 which func-tions as a buffer and LED driver. Allfour signals are visualized by LEDs.The adaptor is best connected to thesystem under test via a set of smallclip -on probes, as shown in the intro-ductory photograph. In a number ofcases, the adaptor may be connectedin parallel to the relevant lines in thesystem under test. That can be doneby virtue of the high current capacityof the HCT541. In effect, the 541's sig-nals will simply override the clock andRST signals in the system.

The 5-V supply voltage for the testadaptor should be taken from the sys-tem under test, and connected perma-nently before the latter is powered up.Separate supplies must not be usedbecause the order in which the circuitsare switched on then becomes an im-portant factor to the microcontroller.

Connecting up to the80C32 SBCTo illustrate the practical use of thetest adaptor, we use the popular`80C32 single -board computer' (SBC)described in Ref. 2 as an example.Interspersed with the descriptionsbelow are hints on how to use the testadaptor with other microcontrollersystems.

RESET connectionMany microcontroller systems have a`reset' push-button, which pulls theprocessor's reset input, or a control

III

IC1

18

R2 17

4/-41-

D2 10012

4700R3 16

D4 0-1 100411:1

91-191111---Laaj---41-

3

4

5V®+

13D3 R6

++LEM

12

5

C4®5V

1I4t16V

CL6

1087.16V 11

6

7

11

12

9

10

9

EN

74HCT541

419

4C?=

107 516V

R8

1k

Cl,

IC2

T1111

R1 OUT

R2OUT

T2IN

MAX232C2 -

V -

T1OUT

R2IN

T2OUT

16

14

13

8

7

K1

02_0

03_0

05 107I=1

6V 1100n

CLK 0 RST

C6

R9

RN 010716V

5V

5V

4

9

5

0-0

0

O co0IC

0C1

0

IN 0 0 TRIG 940117 - 16

Fig. 1. This simple test adaptor, plus a clever program running on a PC, allows every step,however fast and misguided, of an 8051 -type microcontroller to be traced.

input of a watchdog circuit, high orlow. The test adaptor is connected di-rectly to the reset input of the relevantsystem. The software allows the userto determine the length of the resetpulse, and select between an active -high or active -low reset pulse level.

The 'case' for the 80C32 SBC looksas sketched in Fig. 2. The adaptorcontrols the reset input by charging

RESET

measurementadapter

CLOCK

TRIGGER

INPUT

74HCT240

220

Vprobe

I=1

EPROM

AO..A7

A

address -latch

74HCT573

RESET

XTAL1

80C31

XTAL2

PSEN30- ALE

ADO. AD7

P2.0...P2.7

AS.A16 940117 - 19

Fig. 2. Connecting the analyser to the testadaptor.

and discharging a capacitor. The (sim-ple) logic analyser incorporated in thesoftware which runs on the PC has ad-justable safety margins as regards thelength of the reset pulse. This is doneto make sure that the processor is outof its reset state when it is clocked andmonitored. During reset, the softwaregenerates the clock pulses needed bythe 8051/80C32.

CLOCK signalThe clock signal supplied by the adap-tor is used to clock the processor inthe system under test, see Fig. 2again. In most cases, an externallyconnected quartz crystal is used tosupply the system clock in conjunctionwith the on -chip oscillator. TheCLOCK output of the adaptor is simplyconnected to one of the quartz connec-tions. With the 40 -pin DIL package8051, pin 19 is recommended.Different pin numbers may be have tobe used with other (N or C-MOS)processors. Use the data sheets tomake sure of the connection.

TRIGGER inputIf an 8051 -based system is under test,this input should be connected to thePSEN line of the processor. The logicanalyser software uses the trigger sig-nal to start the actual measurementand analysis. The software allows youto select between a high or low triggerlevel. With the 8051, 'trigger -polaritylow' is selected because any programmemory access is flagged by PSENgoing low. With other controller sys-tems, a connection to the read or writeline may be useful.


24 COMPUTERS AND MICROPROCESSORS

Fig. 3. This is how an 8051 should read froman EPROM.

INPUT connectionINPUT is the test probe proper of theanalyser. It is used to connect to vari-ous signals in the system, one at atime, for analysis on the PC. For in-stance, all data bus or address buslines can be picked one by one. Thanksto the advanced storage and displayoptions of the analyser software, thesesignals (17, plus CLOCK) may bewatched simultaneously on the PCmonitor. That enables you to see ex-actly which data is present on the busat a specific time. Switch S1 is used toset the non -actuated level of INPUT,for instance, if it is connected to a busline which can go into high -Z state. Inposition 'high', the analyser sees alogic high level. In position 'AUTO', itsees the CLOCK signal. In this way,the analyser software is capable of es-tablishing that a line is in high -Z state.

Mini logic analysersoftwareThe simpler the hardware, the morepowerful the associated software. Thetest adaptor is linked to the PC via astandard RS232 cable with pin -to -pinconnections. The test probes are notconnected yet, because the softwarehas to be started first. The analysersoftware on being run starts by loadinga configuration file (if found), whichcontains the selected operating para-meters. Next, the analysis is started.Since the test probes are not con-nected yet, the software reports a trig-ger error. Now press some keys to seethe main functions of the test system.Type ? to get a list of the availablecommands and functions, and also togo into adaptor test mode, whichshould be run before hooking up theprobes to the microcontroller system.On returning to 'normal' mode, you areready to commence the measurementproper.

The measurement cycle

The measurement cycle starts by actu-ating the RESET line. In our example,the reset line must be active low. Next,the PC waits a period of which thelength (in ms) is set by the RESET -ONparameter. The delay serves to awaitthe charging or discharging of a capac-itor which is nearly always present onthe reset line in the system under test.Next, the PC generates clock pulses,because most microcontrollers, in-cluding the 8051, require a clock sig-nal to complete the reset cycle. Thenumber of clock cycles produced bythe PC is defined by the value of theRESET -CYCLES parameter. You canalso define whether a clock cyclemeans 'low -to -high' or 'high -to -low'.Next, the measurement proper starts

with the so-called PRE -TRIGGERphase. Clock cycles are then generatedby the PC. After changing the level onthe CLOCK line, the PC waits a shortwhile before measuring the levels ofthe TRIGGER and INPUT lines. Therelevant values are written into thePC's memory. The RESET line is heldlow (actuated) for a period whoselength corresponds to the value as-signed to the RESET -CYCLES parame-ter. The pre -trigger phase ends whenthe TRIGGER level drops low. Fromthen on, the processor is running.

The signals measured from then onare captured, stored in the PC's mem-ory, and displayed later. If the triggersignal fails to toggle after a certaintime, (TRIGGER-TIMEOUT), the PCends the pre -trigger phase of its own.

After triggering, the RUN phase

PORT:COM1 WINDOW:0 CURS:73 PRE -TRG:10

T

I zzzz----

LA 00 01 02

TD 02 02

02 03 04

03 03 05 DO

0

MC 111111111111111111111111222222222222222222222222333333333333333333333333

ADR 0000 0001 0002

0 zzzzzz

1 zzzzzz____ zz zz zz---- zz 0

2 zzzzzz zz zz zz zz____ zz----_-0__

3 zzzzzz zz zz zz zz zz 0

0002 2003 2004

zz zz_______O__

4 zzzzzz zz zz zz zz zz____---1--

6 zzzzzz__________zz_ zz _zz ZZ_ zz

6 zzzzzz zz zz zz zz____--1--

7 _____ _____zz_____ _____zz__________zz____--1--

B

D

E

F

G

H

H..A=04H 7..0=D0H H..0 :04D0H

STOPPED ENTER ? FOR HELP

0

_______O__

_____ 1--

0

0

0

0

0

940117-11

Fig. 4. Screendump produced by the Analysator software. The object is a 80C31starting the EMON51 monitor.

processor


DEBUGGING 8031/8051 MICROCONTROLLER SYSTEMS

starts. The PC continues to supplyclock pulses. The number of thesepulses is defined by the STORAGEDEPTH parameter - the maximumvalue is 3,000. The levels measured bythe TRIGGER and INPUT probes arecaptured and stored into the PC'smemory.

Next, the display phase is started.The chronograms for CLOCK, TRIG-GER and INPUT are displayed on thetop three lines of the screen. The linesbelow show memorized signals labelled0 through 7, and A through H. To copythe current INPUT signal to, say, mem-ory '6', simply press the correspondingnumber on the PC. To be able to viewall eight datalines at the same time,start by sampling databus line DBO,until a stable signal is obtained on thePC screen. Next, copy the signal to

memory '0'. Do the same for the otherdatabus lines, copying their timing di-agrams to the respective memories.

A cursor function is available to geta better view of the state of a numberof signals at a specific time. The cur-rent level of the lines is marked by a '1'or a '0' at the cursor location. Theupper line on the PC screen shows thestate of the eight signals 0 through 7or A through H in hexadecimal nota-tion, allowing single addresses anddata to be traced in a comfortable way.The entire screen can be scrolled hori-zontally to enable the results of longertest periods to be examined also.

High -Z recognitionBus lines in microcontroller systemscan be switched high, low or to a high -impedance (high -Z) state. To be able to

PORT:COM1 WINDOW:0 CURS:73 PRE -TRG:10

I zzzz - - - -

LA 40 40 40

TD FE FE FE

42 42 42

0

FE FE FE

MC 111111111111111111111111222222222222222222222222333333333333333333333333

ADR 0040

0

0040 0002

1 zzzzzz____

2 zzzzzz____

3 zzzzzz____------zz____------zz____

0002

zz zz

zz _

0043 0004

0

zz 1-

zz____ zz____---1--

4 zzzzzz____ zz____ -zz____ -zz____

5 zzzzzz____

6 1-

7 zzzzzz____- - - ---zz____ - - --zz____ - --zz____ - ---zz____ - - - -zz____ ---I - -

A

B

C

E

H

0

-----------------------------1--

H..A=42H 7..0=FEH H..0 :42FEH

ENTER ? FOR HELP

0

0

0

0

1

0

940117-12

Fig. 5. The same as Fig. 4, but this time with two (purposely made) hardware errors on theboard.

detect the latter state reliably, aslightly better measurement method isactually required than offered by thepresent test adaptor. Fortunately,there is a trick to overcome the adap-tor's limitation in this respect.Assuming that there are no propaga-tion delays, a logic signal in a micro -controller system can only change on aclock transition, while it remainssteady during a clock cycle. With S1set to AUTO -Z, and INPUT connectedto a bus line in high -Z mode, the levelat INPUT changes in the middle of theclock cycle. Provided AUTO -Z is se-lected, the analyser software is capableof detecting this, and putting a z at theappropriate location on the PC screen.In this way, open -circuited IC inputsare also detected. It should be noted,however, that the high -Z detectorfunctions only if the 'cycle' has beendefined properly (low -high or high -low). Because of their relatively high -value pull-up resistors, port lines ofthe 8051 which produce a 1 (highlevel) are also marked as 'high -Z'.

Example analysisAn example analysis will be carried outon a properly working 80C32 SBC fit-ted with an AMD 80C31 controller andan EMON51 system monitor. The firstinstructions executed by the processorare

0000 0 2 0 2 0 3LJMP 2 0 3H

0203 7 5DOOOMOV PSW, #0

The timing diagram in Fig. 3 showshow an 8051 gets access to the con-tents of an EPROM. Provided no reador write operation is performed in theexternal data memory, two programmemory access operations occur inevery machine cycle. Each machinecycle has a length of 12 clock oscillatorclock cycles. An MCS-51 instructiontakes either one or two machine cycles(except the MUL and DIV instructions).So, a memory access operation takessix oscillator periods. During the firstperiod, the databus is in high -Z mode,while ALE and PSEN are logic high.During the next two periods, the lower -order address byte is switched to themultiplexed data/address bus. WhenALE has dropped low, the value isstored in the address latch during pe-riods 3 through 6. During periods 4, 5and 6, PSEN drops low also, whichmarks that the EPROM has actuallycopied its data on to the databus.

Let us continue to trace the individ-ual instructions with the aid of thescreendump shown in Fig. 4. To assistin understanding what the multitudeof data is all about, the lines LA (loweraddress), TD (transferred data), MC(machine cycle) and ADR (address)



Fig. 6. Track layout and component mounting plan of the printed circuit board designed forthe test adaptor (board available ready-made through the Readers Services).

were added manually. The first line, C,shows the clock signal of the 80C31.Then comes the PSEN signal on the T(trigger) line. The INPUT line, I, showsthe ALE signal. Memory lines 0through 7 contain the levels capturedon the multiplexed address/data bus.Signals A through H show the eightlow -order address lines of the EPROM.The first access to the EPROM for thefirst instruction starts on the thirdclock period. This instruction, LJMP(opcode: 02), is read from address0000 in the EPROM. During the nextEPROM access operation, the 80C31fetches the first (high -order) byte of thejump address from address 0001 inthe EPROM. Next, the second machinecycle of the LJMP instruction starts.During the first EPROM access opera-tion of this cycle, the low -order byte ofthe jump address (value: 03H) isfetched from EPROM address 0002.The second access is a dummy opera-tion, again fetching the code 03H fromaddress 0002. These dummy opera-tions are typical of the 8051 family ofmicrocontrollers, and tend to compli-cate the reading operations for the de-sired signals.

During the next machine cycle, theinstruction MOV PSW,#0 is executed.The next two EPROM access opera-tions transfer the bytes 75H and DOHcorrectly. The complete address cannot be determined on the basis of thedisplayed signals, because the high -order address byte is not captured. Ifdesired, that may be done in a second

pass, which is not difficult. Before thatis done, however, it is recommended torun a thorough check on all addresslines during the first EPROM accessoperation. As you can see, the systemallows each step of the microcontrollerto be traced with great accuracy.

Finding the errorLet us deliberately create a fault on the80C32 SBC, and see what happens ifwe hook up this board to the presenttest system. Looking at multiplexedaddress/data bus as part of the analy-sis shown in Fig. 5, it is seen that ADOremains low all the time, and AD6,high. Apparently, these lines never gointo high -Z state. And that, youguessed it, pinpoints the errors on theboard: address line ADO is short-cir-cuited to ground, and AD6 to +5 V.Incidentally, the high -order addresses(port P2 of the 80C31) must always beat OOH.

Now let us see what the processor isactually doing during the first few cy-cles. The first ALE -low conditioncauses a value 40H to be written intoaddress latch. Although the 80C31 hasproduced the value 00, the perma-nently high level of AD6 causes awrong address to be copied to the ad-dress latch. Although the EMON51EPROM contains the value 'FFH' at ad-dress 40H, the processor actuallyreads back `FEH' because ADO is per-manently low. The opcode OFEH hap-pens to mean: MOV R6,A, is one

0

Resistors:R1;R3;R5;R6 = 4700R2;R4 =11d2

Capacitors:C1;C7 = 100nFC2 -C6 = 10uF 16V radial

Semiconductors:D1 -D4 = LED, 3mmIC1 = 74HCT541IC2 = MAX232

Miscellaneous:K1 = 9 -way Sub -D socket, PCB mountS1 = miniature switch, SPDT, PCBmount, or 3 -way jumperPCB and software on disk: order code940117-C (see page 70).Software on disk also available sepa-rately, order code 946203-1 (see page78).

machine cycle long, and occupies onebyte. Consequently, the secondEPROM access operation in the firstmachine cycle is nothing but adummy. Next comes the second ma-chine cycle, which yields the secondinstruction. At this stage the instruc-tion counter in the 80C31 reads '1'.However, since ADO is at 0 all the time,the address latch is again loaded withthe value '40H'. Subsequently, anotheropcode 'OFEH' is fetched. The dummymemory access operation with this in-struction, by the way, is to address42H this time, as a result of thechanged state of the instructioncounter. This address in the EPROMagain contains 'FFIT, which is read as`FEH' by the processor. Another`MOV R6,A' instruction is executedwithout making any sense. This con-tinues endlessly until the hardwarefault is removed and the system isreset.

As shown above, apparently simplehardware errors may cause rare andvery hard to understand signals. Thatis why there is a golden rule in micro -controller debugging: if you find ahardware error, eliminate it. Do not tryto understand what it does to the soft-ware; pursuing that cause is often triv-ial and a waste of time.

Finally, those of you who are strug-gling with a faulty 80C32 single -boardcomputer running the EMON51 moni-tor may use the screendump in Fig. 4as a reference to see how the systemshould start up after a reset.



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Other applicationsDebugging an 8051 -based microcon-troller system often involves testingRAM and port access operations also.Here, it pays to use an EPROM emula-tor into which a short test program isblown. To test port P1, for instance,the following little program is used:

start INC P1

SJMP start

Similarly, check write operations to,say, address 2345H with the aid of thefollowing program:

start MOVMOVMOVXSJMP

DPTR,#2345HA,#0A5H@DPTR,Astart

In some cases, it is desirable to viewmore cycles at the same time.Fortunately, that is catered for by theprogram.

The operation of the 800535 sin-gle -board computer (Ref. 3) can beanalysed without problems using thepresent system if you set the 'cycle' de-finition parameter to LOW -HIGH, andinject CLOCK at pin 39 of the CPU.

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The use of the Analystor' program andthe associated measurement adaptoris not limited to microcontrollerboards. In fact, the tester may be usedwith almost any logic circuit which canbe made to work from an externallyapplied clock. In the worst case, a PCBtrack or two may have to cut to enablethe clock signal to be injected. Circuitsthat can be analysed and debugged inthis way. include those containingcounters, PALs or GALs.

It will be clear that the present de-bugging system is simple, and will notenable you to find any error `spot-on'.With a little dexterity, however, most,if not all, malfunctions can be recog-nized. A broken PCB track, for in-stance, may cause one and the samesignal to look different at two differentpoints in the circuit. So, check if two(supposedly) equal signals are actuallyequal. Short-circuits between data buslines may also be quite elusive andpose baffling problems.

Construction

The test adaptor is best built on theprinted -circuit board shown in Fig. 6.This board and the associated

Analysator software is available ready-made through our Readers Services.The board is fitted in a small plasticbox. The 'external' elements are the 9 -way sub -D socket, switch Si, wires forthe 5-V supply from the system undertest, the four probe wires and the asso-ciated LEDs. (940117)

References:1. 80C32.8051AH-BASIC Single -boardcomputer, Elektor Electronics May1991.2. Short course 8051/8032 microcon-trollers and assembler, ElektorElectronics (Publishing) book, ISBN 0905705 38 6.3. 800535 Single -board computer,Elektor Electronics February 1994.

More on the same subject:Debugging the 8031 series, ElektorElectronics November 1994.


28

SELF -LOADING EEPROM TYPEX88C64

Xicor's X88C64 SLICTM (self -loading integrated code) IC is an8Kx8 EEPROM with an internal address decoder and amultiplexed data/address bus. The memory consists of twoindependent arrays with a size of 4Kx8. Another specialfeature of the SLICTM is that it has a non-volatile codedownloader which makes program development a lot easier forthe popular 80xx and 68xx microprocessors.

By our editorial and design staff. Source: Xicor Inc.

COMPLEX and expensive develop-ment tools never seem to have

boosted the popularity of any micro -controller. In general, the easier -goingthe software development and debug-ging tools, the wider the acceptance ofa particular device. Arguably, anEPROM emulator is the cheapest de-velopment tool which can be used al-most universally. One side of theemulator is connected directly to thesocket for the EPROM which containsthe system software. The other side isconnected to a PC which is used to(cross-) assemble, debug, and down-load machine code to the emulator,using, for instance, the Jedec, IntelHex

or Motorola file formats.Although an EPROM emulator is a

cost-effective and fairly easy to handlesoftware development tool, there areeasier solutions. Xicor, with the intro-duction of its X88C64 SLIC EEPROM,shows the way.

Essentially, a microprocessor sys-tem in which SLIC routines are usedcan be programmed via the regular se-rial interface. The SLIC contains acompact library of routines which are,in principle, started automaticallyafter a reset. The only requirement asregards the machine code is that a 3 -byte code block ('header') is transmit-ted before the data. Software is

available for MS-DOS PCs to makeIntelHex files compatible with the SLICprotocol.

Both 4-K memory arrays inside theX88C64 contain SLIC routines.Version Beta 2.1 has 256 instructionsin the upper part of the memory bank(1FOOH - lEFFH), and 240 bytes in thelower bank's address range, just abovethe interrupt vectors (0030H - 011FH).The address division is shown inFig. 1. The user's application codeshould avoid these areas as part of itscode segment, otherwise it will over-write the SLIC. All user programs mayuse the memory segment between0120H and 1FOOH.

The SLIC programming routinesform part of the software, and may befound in both memory arrays. Duringprogramming, the EEPROM arraywhich is not in use is not accessible forabout 5 ms. Consequently, softwarefrom the other array has to be usedduring that period. The X88C64 comeswith the reset vector at address 0000Hpointing at 0030H, so that the proces-sor jumps to the start of the SLIC seg-ment after a reset. To enable your ownprogram to be launched at power -on,this reset vector has to be overwritten.

To be able to use the SLIC routinesagain after overwriting the reset vec-tor, the user program has to providefor a jump to these routines.Alternatively, some code may be addedto the user program to enable the SLICroutines to be started via, for instance,INTO or INT1. If you forget to includesuch a routine, the SLIC is gone for-ever (well, almost) after programming,so take care! Do not download 'any'program to make your first acquain-tance with the X88C64. Familiarizeyourself with this new device in a step-by-step manner, making sure at alltimes that the SLIC routines are notoverwritten.

Re-entering the SLIC segments intothe EEPROM banks of the X88C64 re-quires a dedicated programmer whichis capable of supplying special codes,and using the multiplexed data/ad-dress bus. Copies of the SLIC routinesare supplied on disk with the EEP-ROM.

ConditionsThe data sent to the SLIC softwaremust meet a number of conditions. Tobegin with, a 3 -byte header must be


SELF -LOADING EEPROM TYPE X88C64 29

transmitted. The headers should con-sist of:

- command type identifier;- total number of bytes in data block;- starting memory address (LSB first).

The subsequent data must lie in thesame memory block (page) of 32 bytes.The databytes are read by the soft-ware, and stored into the internalRAM. Next, all interrupts, includingthose of the UART, are blocked. Then,the data is copied to the EEPROM.Programming the entire block takesjust as long as programming a singlebyte. During programming, all datatransmitted to the UART are lost.Hence, new data may not be transmit-ted until the SLIC software reportsthat it has finished programming. Thisis indicated by returning a `D' (for`done').

The protocol is fairly complex be-cause the EEPROM can not be read ifdata is being written into the sameblock. If data is being written into thelower block (0000H), the processormust fetch its instructions from theother block (upper part of the mem-ory). Since the vectors, like the in-structions, are stored in EEPROM, it isnot possible to read them during pro-gramming (notably the UART vectors).That also explains why the serial linkis 'temporarily out of order' during pro-gramming.

The SLIC software remains intactafter you have changed the interruptvector. The first thing it does on beingactuated is reprogram the UART inter-rupt vector. This re -programming op-eration is performed after each reset,power -up, or call to the SLIC program.There is one limitation, though: ac-cording to Xicor, the maximum num-ber of erase/write operations on anEEPROM memory location is 10,000.

The complete systemThe SLIC program written by Xicor hasa size of about 500 bytes, and consistsof two parts. The part in the lower halfof the EEPROM is capable of program-ming the upper half, and vice versa.EEPROMs with the code `SLIC' printedon them have these programs. EmptyEEPROMs are also available fromXicor.

You are ready to start programmingas soon as the EEPROM is fitted intothe system. Set your PC or terminal for9600 baud, 8 databits, no parity and1 stopbit. Commands are issued bytransmitting an ASCII character to theSLIC. These characters may be termi-nated with a carriage return (CR), al-though that is not strictly necessary.The SLIC responds as described below.Usually, it does not generate a CR; and

1FOOH

0120 H

0030 H IIII+

0000 H

SLIC

User's program

SLIC

ISR and reset -vectors

940116-11

Fig. 1. EEPROM memory division.

never a line feed (LF). The SLIC routineis started after a hardware reset. First,a 'D' is returned to the PC. If you donot see this character, there is some-thing wrong in the system.

After the reset (hardware or soft-ware), the following command must al-ways be sent:

Command: XResponse: X88C64:132.1 (CR)The SLIC responds to this commandby returning its version number (here:Beta 2.1) after a colon. Next, one of thefollowing commands may be sent:

Command: MxxxdataResponse: DProgram (Modify) the contents of theEEPROM. The capital M must be fol-lowed by a byte (represented by thefirst `x') which indicates the number ofbytes to be programmed. The second`x' represents the LSB (least -significantbyte) of the programming address. Thethird 'x' is the MSB (most -significantbyte) of the address. Next come thedata. Any number between 0 and 255is transmitted as a byte. There is noerror detection or correction.

The following points should be ob-served when programming. The num-ber of bytes may be between 1 and 32.If you program a single byte, any ad-dress may be given. If you programmore bytes, the SLIC routine will firstreceive them and then store them in abuffer. Once all bytes are received, theEEPROM is programmed in `page'mode. In this time -saving mode, up to32 bytes are sent to the EEPROM, andprogrammed in one go within 5 ms.This system works properly if the data-

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

940116.12

Fig. 2. Example of an IntelHex file. This is actually the code contained in the SLIC.


30 COMPONENTS

WRITE AATO X555

WRITE 55TO XAAA

WRITE AOTO X555

PERFORM BYTEOR PAGE WRITE

OPERATIONS

WAIT t WC

EXIT ROUTINE

0

X = Al2

Al2 = 1 IF DATA TO BEWRITTEN IS WITHINADDRESS 1000 TO 1FFF

Al2 = 0 IF DATA TO BEWRITTEN IS WITHINADDRESS 0000 TO OFFF

940116 - 15

X88C64 SLIC EEPROMXicor's X88C64 EEPROM has a couple of features which set it apart fromother EEPROMs. The main difference is the multiplexed address/data bus,which enables the device to be connected directly, without a latch, to theprocessor bus of 8031 -series processors. Xicor also supply the X68C64which is designed to connect to 68xx processors such as the 68HC11. TheEEPROM consists of two 4Kx8 memory arrays which can be individuallyread and programmed. There are two ways to protect the data in thememory:SDP, protection via software This serves to prevent bytes beingoverwritten by accident. Programming is only allowed after three pre-defined bytes have been written to three pre -defined addresses. See theflow diagram in Fig. A.BPR, extra protection of parts of the EEPROM (chunks of 1 KByte each).This is achieved by writing five pre -defined bytes to five pre -definedaddresses. See the flow diagram in Fig. B.Internally, the EEPROM consists of two independent arrays which can beread and programmed without affecting one another. To enable themicrocontroller program to be modified without removing the EEPROMfrom its socket, a system configuration as shown in Fig. C has beendesigned. The structure of the processor-EEPROM interface is such thatALE, PSEN, WR and RD are all used. Apart from reading instructions withthe aid of the PSEN signal, it is, therefore, also possible to write data tothe EEPROM (because of the presence of WR). Reading data isaccomplished with the aid of the RD signal.

The EEPROM actually consists of two 4Kx8 EEPROM arrayswhich will be referred to as 'upper' and 'lower' for the sakeof convenience. When he processor is busy readinginstructions from the lower array, the upper array is notused, and may be programmed. Programming takes amaximum of 5 ms, during which it is not possible for themicroprocessor to fetch instructions from the relevant array.As already mentioned, programming always takes placewithin the bounds of a page, i.e., 32 bytes. As soon as a

byte is writtenwithin such apage, theinformation isstored in alatch inside theEEPROM. Theprocessor maythen write thenext byte tothe same page.The bytes mayarrive withintervals of acouple ofmicroseconds.If no newinformation iswritten into thememory pagewithin 100 ps, the actual programming operation commences. During thisoperation, the EEPROM is not accessible for a period of up to 5 ms Inpractice, programming will take less than 5 ms. Hence, a protocol isincorporated which checks if the programming is finished. The level on dataline 6 toggles during programming. The programming operation is finished ifthe same level appears twice in succession on the line.

O

80C31

PO 0

PO 1

PO 2

PO 3

PO 4

PO 5

PO 6

PO 7

P2 0

P2 1

P2 2

P2 3

P2 4

PSEN

ALE

RD

WR

P2 7

EA/VP

X1 X2

.24

39 7

38

37 9

36 10

35 11

34 13

33 14

32 15

21 21

22 20

23 17

24 19

25 2

29

30 22

17 18

16 23

28 16

19

31

NJ

v 00

ADO

AD1

AD2

A03

AD4

ADS

AD6

AD7

X88C64A8

A9

A10

All

Al 2

PSEN

ALE

RD

WR

CE

WC

940116 - 17

OWRITE AATO X555

WRITE 55TO XAAA

WRITE AOTO X555

(BPR REGISTER SET)

EXIT ROUTINE

X = Al2

Al2 = 1 IF PROGRAM BEING EXECUTEDRESIDES WITHIN ADDRESS 0000 TO OFFF

Al2 = 0 IF PROGRAM BEING EXECUTEDRESIDES WITHIN ADDRESS 1000 TO 1FFF

940116-16



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COMPONENTS

REM SIMPLE TEST FOR SLICCLOSE #1CLSOPEN "COM1:9600,N,8,1" FOR RANDOM AS #1PRINT "PLEASE PUSH RESET BUTTON"PRINT INPUT$(1, #1); " RECEIVED"PRINT "SLIC IS ALIVE, NOW ASKING FOR ID"PRINT #1, "X"PRINT "WAITING FOR RESPONSE..."ID$ = ""WHILE RES$ <> CHR$(&HD): REM UNTIL <CR>RES$ = INPUT$(1, #1)ID$ = ID$ + RES$PRINT ASC(RES$);WENDPRINT : PRINT "THE ID IS "; 1D$

PRINTPRINT "NOW WE DO SOME PROGRAMMING"REM IF YOU CHANGE NEXT LINE REMEMBER LSB OF ADDRESS FIRST!!PRINT #1, "M"; CHR$(3); CHR$(&H30); CHR$(5); CHR$(&H12);CHR$(34); CHR$(56)PRINT "WAITING FOR RESPONSE"RES$ = INPUT$(1, #1)PRINT "RECEIVED IS ";PRINT RES$; "("; ASC(RES$); ")"

PRINTPRINT "VERIFICATION OF PROGRAMMED BYTES"PRINT #1, "V"; CHR$(3); CHR$(48); CHR$(&H5); CHR$(18);CHR$(&H22); CHR$(56)PRINT "WAITING FOR RESPONSE"RES$ = INPUT$(1, #1)IF RES$ = "F" THEN PRINT "F RECEIVED, VERIFICATION FAILED"IF RES$ = "D" THEN PRINT "D RECEIVED, VERIFICATION O.K."

CLOSE #1940116.13

Fig. 3. A BASIC program which enables the PC to communicate with the SLIC software in an8031 -based microcontroller system.

bytes are intended for addresses whichfall into one page. This is the case aslong as address lines A5 through A I 2

remain at the same level. So, take carewhile programming more than onebyte that only address lines AO -A4 are

allowed to change.On completion of the programmingcycle, the SLIC software returns a 'ID'(done). Note that this message onlymeans that the programming opera-tion has been completed. it should notbe taken to mean that the data hasbeen programmed correctly.

Command: VxxxdataResponse: D or FThis command verifies the contents ofthe EEPROM against the serial data -bytes. It is largely similar to the 'pro-gram' command. Here, too, receivedbytes are placed into a buffer, andmust fall within the same page. TheSLIC responds with 'D' (done) or 'F'(fault).

Command: RResponse: DReset command. The X88C64 runs itsinternal power -up routine and on com-pletion returns a 'D' to the PC. Next, itwaits exclusively for 'X'. No responsewill be given to another reset, a pro-gramming or verify command.

Command: KdataResponse: noneThis command serves to modify thecontents of the BPR register. 'Data' in-dicates the byte written into the BPRregister. This determines which blocksare accessible for programming. Eachbit determines the 'programming al-lowed/disallowed' status of a 1-Kblock (0 = programming allowed; bit 0is the block with the lowest address).

Fortunately, Xicor supplies a PC pro-gram with its SLIC EEPROMs to takethe hassle out of the communicationprotocols described above. The currentversion (3.34) allows the user to selectthe COM port used on the PC. Updatedversions of the control software may bedownloaded from Xicor's bulletinboard in the U.S.A. The number is (+1)408-9430655.

The software on being started tellsyou straight away if communicationwith the SLIC is possible. If not, go tothe setup menu, and select the rightcommunications port. The program re-quires input data in IntelHex format,which will be available in most casesbecause it is accepted by most EPROMprogrammers. The structure is fairlysimple: a line starts with a colon. Thenfollow a number of bytes, the address,a code, the databytes, and, finally, achecksum. Figure 2 shows a part ofsuch a file.

Since a couple of devices in the8051 family of microcontrollers havevectors above 0030H, the control pro-gram is capable of moving the SLICsegment to address 0080H. Those ofyou who wish to experiment may find


SELF -LOADING EEPROM TYPE X88C64

P*1

5V

5V

0

K1

0

K2

5V 0

s, 7

RESET?

3

000000

C1

16V

P1071

40

9

P12 P12

P13 P13 4

7 P14 P14

P15\iP 15 6

P16\*./P160 P17 v P17 8

3 P30 P30 10

O

O

OOOO

31 P3

P32 P32 12

7

P33N.."1,33 13P34Nm/P34 14P35 N..435 15P36 P36 16

5V ®

0

R3

R4

K53 4

A. k33052 330/

R6

R5

P37 \.../P37 17

RESET

P1.0

P1.1

P1.2

P1.3

P1.4

P1.5

P1.6

P1.7

TXD

INTO

INT1

TO

T1

WR

RD

IC1

80C31

1 X1

PO.0

P0.1

P0.2

P0.3

P0.4

P0.5

P0.6

P0.7

P2.0

P2.1

P2.2

P2.3

P2.3

P2.5

P2.6

P2.7

ALE/T,

PSEN

EANT,

X2

39

..L13 .112

:00n :100n 24

38 8

37 9

36 10

5

34

33 14

32 5

1 2

22 2

23

24 1

25 2

26

27

21

30 22

29 6

20 119 X1

C4

18

C3

277 77pX1 = 11.059MHz

2

2//

12

S2 C2OINTO 16V

_410g1IC4

*see text

D1

1N4001K4

5V

O

C11

10µ16V

TXD

C6

H10p16V

ADO

AD1

AD2

AD3

AD4

ADS

AD6

AD7X88C64

XICORA8

9

Al 2

IC2

ALE

PSEN

WR

RD

WC .6 CE5 112 16

C9 L1 5V

016V

C7

07r IC3

16VR2OUT R2IN

° T2IN T2OUT

RXD 12

CO

10.16V

3

T1IN T1OUT

R1OUT R1IN

MAX232

v-

6

10.16V

16

8

7

K3

14

13

O

O

O

0

O

940116 - 14

Fig. 4. Circuit diagram of a small 80C31 controller system which incorporates an X88C64SLIC EEPROM for time -efficient program development.

the BASIC program listed in Fig. 3 ofinterest.

The rules of the gameRecapping, observe the following ruleswhen using the SLIC routines:

(1) Supply an IntelHex file.(2) Do not allow data to cross page

boundaries.(3) Ensure that memory areas 0030H-

011FH and IFOOH- 1 FFFH are notoverwritten, because they containthe SLIC.

(4) The UART vector (0023H in the

8031) should be re -programmed inthe last line of the IntelHex file.

(5) Place a jump to the start of theSLIC code (JMP 0030H) at the INTOvector address (0003H), and do notforget to enable the INTO interrupt(bit register EX0=1), and to enableall interrupts (bit register EA=1).

All of this may look pretty complex atfirst. However, after a while you willbecome conversant with the program-ming techniques. Those of you wholike (Visual) BASIC or Pascal program-ming may write a small program whichkeeps an eye on the above rules, and

supplies alerts where necessary. Thedocumentation contained in the SLICdesign package also points out that alarger part of the 500 bytes of SLICprogram may be incorporated in theuser program (for instance, the UARTroutine). In this way, the SLIC neednot be 'ballast' only.

The SLIC design pack supplied byXicor contains the X88C64, adatasheet, application notes and adiskette containing the above men-tioned control program and the sourcecode of the software in the EEPROM.

SLIC demonstration boardFigure 4 shows the circuit diagram ofan 80C31 processor board based on anX88C64 SLIC EEPROM. The circuitalso contains a MAX232N RS232 dri-ver/interface for the link to the PC,and an I2C interface plus socket. Itshould be noted that the 80C31 has nobuilt-in I2C software. However, thatcan be downloaded from the PhilipsBulletin Board in Eindhoven, TheNetherlands. The number to dial is(+31) 40 721102.

The quartz oscillator crystal fre-

COMPONENTS LIST

Resistors:R1;R2 = 10052R3;R7 = 31(123

R4;R5;R6 = 330Q

Capacitors:C1 = 2pF2 16V radialC2;C5-C9;C11 = 10pF 16V radialC3;C4 = 27pFC12;C13 = 100nF

Inductor:L1 = 100pH

Semiconductors:D1 = 1N4001IC1 = 80C31IC2 = X88C64SLIC (Xicor)IC3 = MAX232NIC4 = 7805

Miscellaneous:K1;K2 = 10 -way boxheader.K3 = 9 -way sub -D socket, angled pins,PCB mount.K4 = 2 -way PCB terminal block, raster5mm.K5 = 6 -way mini -DIN socket, PCBmount.S1;S2= MuItiMEC 2CTL2 press -key.X1 = 11.0592 MHz crystal.Printed circuit board 940116 (see page78).


34

CORRECTIONS AND UPDATES800535 Extension card

June 1994, p. 8-11The PCD8584 may be switched to`6800' mode if a WR signal arriveswithout a CS signal. The problem maybe solved by combining WR and CS ina diode -AND gate as shown below.Pin 18 if IC4 is taken out of the ICsocket and connected to ground via a10-kS2 resistor. The WR signal is foundon socket pin 18, and CS on pin 10 ofIC5. Also note that the PCD8584 iscurrently supplied as the PCF8584.

quency, 11.0592 MHz, must not bechanged into, say, 12 MHz because itdetermines the speed of the SLIC serialcommunication (9600 baud). Apartfrom the reset switch, S1, the circuitalso has a press -key to generate anINTO interrupt. If capacitor C2 is mademuch larger than C1, the circuit gener-ates an INTO interrupt automaticallyat power -on. This interrupt shouldcause the system to jump to the SLICsoftware, via the user program.

The I/O lines of ports 1 and 3 areavailable on connectors K1 and K2.These connectors may be used to hookup extension circuits which serve tocontrol the 80C31.

Finally, the track layout and compo-nent mounting plan of the80C31/SLIC board are shown inFig. 5. (940116)

For further information, contactXicor, Inc., 1511 Buckeye Drive,Milpitas CA 95035-7493, U.S.A. Tel.408/432-8888, fax 408/432-0640.Xicor Ltd., Hawkins House, 14 BlackBourton Road, Carterton OX18 3QA,England. Tel. (01993) 844435, fax:(01993) 841029.

Fig. 5. Printed circuit board designed for the80C31/SLIC controller (board availableready-made, see page 78).

Dual-purpose LED display

December 1994, p. 90Resistor R33 should be connected toground, not to +12 V as shown in thecircuit diagram.

Experimentation board forPICsJuly/August 1994, p. 74.In the circuit diagram, the signals onpins 7 and 8 of both connectors K1should be swapped. MCLR is on pin 8,and RTCC on pin 7. The relevant PCBis all right.

Mains signalling system(2)May 1994, p. 10-14.The instructions for command 'T'should read: 'T' must be followed bythe address in ASCII, and terminated

with a semicolon (';').The baudrate for the communica-

tion software should be set to 300, for-mat: 8 bits, 1 startbit, 1 stop bit, noparity.

Electronic fuseMarch 1994, p. 56.To prevent transistor T2 from burningout when the reset switch is pressedduring an overload condition, switchS1 should be connected between thecollector of T1 and the base of T2.



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Elektor Electronics or its consultants.

Selecting voltage referencesA Maxim Application

Voltage references are simple devices,but making the right choice for a given

application can be a chore if you do not takean orderly approach. This article simplifiesthe task with a review of the available ref-erence types and a discussion of the speci-fications manufacurers use to describe them.

Unlike most electronic circuits, the volt-age reference resists any change in output.While most circuits try to produce an idealwaveform or a faithful replica of input vari-ations, the ideal reference maintains constant(Iota despite all variations in time, tem-perature, input voltage and load current.References differ in their approximations ofthis ideal, so to choose well you must be fa-miliar with the available types and theirperformance parameters. These two topicsare covered in the following sections.

Voltage -stable devicesBefore the advent of solid-state voltage ref-erences, engineers in search of a stable volt-age had to use standard cells or batteries.Both are self -powered and produce stable,well-defined voltages when not loaded. But,since their output voltages are so tempera-ture sensitive, they must be specified at asingle temperature.

The standard cell consists of liquid mer-cury and liquid electrolyte in an H-shapedglass container. Though accurate to a few partsper million, it can take weeks or months torecover if overloaded or tipped on its side!

Mercury cells (batteries) are more ro-bust. Good for several years without re-placement, they provide about 21/2 digit ac-curacy when new. They furnish only a fewmilliamps of current. Though still used insome portable applications, most have beenreplaced by modern low -current (10 fA) ref-erences.

The first modern voltage reference is thezener diode. Used mostly in clamp circuitsand power supplies, it comes in a variety ofvoltages, packages, and power ratings. Notquite accurate enough or stable enough toqualify as a voltage reference by itself, thezener produces a reasonably constant volt-age when connected in series with a resistorand a source of unregulated voltage.

The zener's temperature coefficient (tem-pco) is a function of its breakdown voltage,

and is remarkably low at about 6.3 V. By plac-ing a conventional pin junction in serieswith the zener, you get a combination whoseforward voltage drop (at a specific operat-ing current) can be tailored for extremely lowtempcos. Known as a reference diode, thiscombination has seen lots of development.For tempcos below 25 ppm °C-1, however, thecost becomes prohibitive for testing, match-ing, and selecting the diodes.

Zeners have a well -understood ageingeffect, and the best reference diodes receiveyears of burn -in conditioning to minimize theoutput changes caused by ageing. Such de-vices are produced not by the zener manu-facturers, but by specialty houses and man-ufacturers of high -end voltmeters and lab-oratory voltage standards.

The combination of a reference diode andop amp in a hybrid IC produces the ampli-fied diode-a voltage reference with manyadvantages. Rather than testing and match-ing diodes (a procedure involving thousandof logged measurements and hundreds ofparts at dozens of temperatures) you simplycombine randomly selected op amps andreference diodes, and set the tempco withstandard op amp trimming techniques.

Each amplified diode requires a completetemperature sweep followed by several trims,and a second temperature sweep to confirmperformance, but the resulting tempco isbetter than 1 ppm °C-1. Maxim's hybrid ref-erences, the MAX670 and MAX671, are built

1.240

1.235

1.230

1.225

1.220-50 -25 0 25 50 75 100 125

TEMPERATURE (°C)940122-11

and tested in this way.The MAX670/671 amplified -diode refer-

ences use internal resistor networks to am-plify the output to 10.000 V ±1 mV, inde-pendently of the precise zener current andvoltage required for minimum tempco.

In addition, the MAX670/671's opamp isconfigured as a 4 -wire power supply with sep-arate force and sense leads to eliminate theeffect of voltage drops along the connectingwires. As a result, the reference voltage ap-pears exactly where it is needed-not justat the amplified -diode's output terminals(see the box on the next page). This featureis vital to low-ppm applications because iteliminates ground -loop errors, thermal volt-ages, and IR drops in the connections-in-cluding a socket (if used) for the voltage ref-erence itself. (At 1 mA, a 10 rnf trace resistanceproduces a 10 1V [1 ppm] error).

Kelvin connections also allow the deliv-ery of considerable load current. If necessary,you can boost the load current to severalamperes ( without degrading accuracy) byadding an external pass transistor withinthe feedback loop. Thus, the amplified diodenot only eliminates board trimming duringmanufacture, it ensures repeatability-bothon the production line and following field re-pair.

The zener diode's successor is the band -gap reference. Almost impossible to makewith discrete components, the bandgap ref-erence is made practical by integrated-cir-

10m

100p

10p

0.2 0.4 0.6 0.8 1.0 1.2 1 4

REVERSE VOLTAGE (V)940122-12

Fig. 1. The familiar 'S' curve of thisbandgap reference shows a minimum

variation with temperature.

Fig. 2. Bandgap diodes have a muchsharper knee than actual diodes.


SELECTING VOLTAGE REFERENCES

Kelvin -sensed outputsSeparate force and sense paths can greatly improve the perfor-mance of a voltage reference. That arrangement (called a Kelvinconnection) is common in high -accuracy designs, but it also re-moves most of the noise and drift in a reference circuit of mod-est accuracy.

Such a circuit is the 3 -wire, 2.5 V reference of Figure A. Thoughsuitable for use with 12 -bit A/D and D/A converters, it is proneto errors that are often overlooked or dismissed as insignificant.These errors are caused al most entirely by the effects of printed -circuit resistance and poor layout.

Note, for example, that 'ref (10 mA) and /out (100 mA) share aground -return trace whose resistance is represented by R5.Assuming this trace measures only 10 mQ, the resulting direct -voltage error is 1.02 mV-nearly two LSBs in a 12 -bit systemwith a 2 5 V reference.

Resistors R5 and Rs also produce variations in reference volt-age as the reference load varies. These resistances may measureonly 10 mt/ as printed -circuit traces, but the values (and the re-sulting errors) can escalate if the reference is placed in a socket,or if the reference load current passes through an edge connec-tor. Connectors are particularly troublesome because their re-sistances change each time they are reconnected.

Resistors R1 and R3 cause less -obvious problems They do notcontribute direct voltage errors, but fast transients in the high -power load must pass through them The resulting voltage mod-ulation at the reference -supply pins can cause instability in thereference

The circuitof Figure B is similar but offers two major im-provements. First, it isolates the reference and high -power loadsby providing separate paths from the high -power load all the wayback to the battery terminals. High -power load transients nolonger modulate the reference, because the connecting traces (R2and R4) are separate from those of the reference (R1 and R3).

Second, the reference load is Kelvin -connected to its drive cir-cuit The high resistance of RH and RL assures accurate feedbackto the error amplifier, regardless of trace resistance in the senselines (R7 and R6). Moreover, the errors caused by trace resistancein the force lines (Rs and R5) are excluded by the amplifier's feed-back (sense) connections.

Separate force and sense lines allow the reference load andits error amplifier to he separated) if necessary) by lengthy wiresand numerous connectors. Calculations show that the errors inFigure B can be made astonishingly small-so small that littlepenalty accrues ifyou reconnect the high -power load as in FigureA In that case, note that a change in the voltage across R5 (inFigure B) shifts all voltages in the reference circuit, but Ukadremains constant.

Kelvin connections not only compensate for errors that arisein passive components; they also accommodate active compo-nents such as the optional boost transistor shown in Figure B.With that transistor in place (replacing the R8 force line), you can

A!BATT-0106

VBATT

R2

10 IREF

ERRORAMPLIFIER

INTERNALREFERENCE

R3

!OUT .6 HIERRx

= TRACE OR WIRING RESISTANCE

0

R8

VREF 1REF

5

r -REFERENCELOAD

VLOAO = VREF -110E6 R8 - + 1REF)R5

VLOAD

R4

HIGH -

POWERLOAD

1OUT

FOR 10m TRACE RESISTANCES A 10mA REFERENCE LOAD AND A HIGH POWER LOAD,Wm. IS 1 02mV LESS THAN VREF FOR V REF =2 5V THE RESULT ERROR IS 408ppm

900122.16

BR2

MAX670 MAX671.MAX676,MAX677 OR MAX678

R OPTIONAL

Venn

ERRORAMPLIFIER

RR

BOOSTTRANSISTOR

REFERENCE IC

R8FORCE+

INTERNALREFERENCE

VREF

_1

SENSE+

R7

REFERENCELOAD

R6SENSE -

Rx

R5FORCE -R3

R4

= TRACE RESISTANCEOR WIRING

HIGHPOWERLOAD

10UT

Vamp = VREF X (R R+ RL)1 RLO K

K = (RINAL,R7+R6) / (Rn+R = (300 000+100 000+0 01+0 01) / (300 000+100 000) = 1 000 000 05900122 17

increase current -source capability in the reference without de-grading accuracy Similarly, you can increase the current -sinkcapability by adding a p -n -p transistor with its collector connectedto ground.

Finally-the accuracy achieved with Kelvin connections elim-inates the need for board trimming during manufacture The re-sult is repeatable performance, both for the units of a productionlot and for a single unit before and after field repair.

cuit technology. Bandgaps are based on asimple and elegant principle-take a knownproblem and turn it into a solution.

The problem is that forward -conductingsilicon diodes have a well-defined tempera-ture coefficient (2 mV °C-1), but a hard -to -control offset voltage. The solution is to fab-ricate (for example) 11 identical diodes ona silicon substrate, arrayed in a tight groupfor close thermal matching. Connect all butone central diode in parallel. Then, drivethat diode and the remaining group with twoidentical currents, so the central diode op-erates with an approximate 10 -times highdensity across its junction. The central -diode voltage has a negative tempco, but

the voltage difference (for the single diodevs the group) has positive tempco.

If you then arrange for the voltage difference(times a gain factor) plus the central -diodevoltage to equal the bandgap voltage of sil-icon (1.205 V), the sum will (ideally) have atempco of zero (Figure 1). This is what thebandgap circuit does.

The simplest and least expensive bandgapreference is a two -terminal device such asMaxim's ICL8069, which operates like azener diode. Unlike zeners, however, thebandgap has a low voltage (1.23 V) and a verysharp knee at low operating currents: thevoltage change from 50 fA to 5 mA is less than15 mV (Figure 2). Low voltage and low cur-

rent make bandgap references suitable foroperation in feedback networks, biasingnetworks for opamps, and other circuits forwhich the zener reference is inappropriate.

SpecificationsTo select the best reference for a given ap-plication, you must be aware not only of thedifferent reference types, but also of spe-cial definitions manufacturers use for the spec-ifications that describe voltage -referenceperformance. The following entries defineand discuss each parameter.Accuracy. This is an ambiguous term. It

is literally the sum of all deviations from


38 APPLICATION NOTE

the ideal output value, expressed as afraction of the ideal, subtracted fromone, and multiplied by 100. A perfect ref-erence, therefore, is 100% accurate. Butin common usage, accuracy and totalerror are used interchangeably. A `1% -accurate' reference is generally under-stood to have a total error of 1%, not 99%.

Error. A particular categeory of deviationfrom the ideal. Voltage -reference errorsare expressed either as absolute values(mV, for instance), or as fractions, andin percent (%) or parts per million (ppm).

Initial accuracy. The output -voltage tol-erance exhibited by a voltage referencefollowing the initial turn -on of power. Itis usually measured at no load or for arange of load currents. In many appli-cations, initial accuracy is the most im-portant specification. For low-cost ref-erences, it may be the only accuracy spec-ification.

Turn -on drift. A change in output voltageover a specified time interval followingturn -on. With or without an oven, all ref-erences exhibit some change over thefirst seconds or minutes following turn -on. Usually asymptotic, turn -on drift isan important specification for portablesystems that conserve battery energy bypowering the reference for short periodsonly.

Short-term drift. Similar to turn -on drift,but specified for a short period (mil-liseconds to minutes) at any time afterturn -on. It often appears in data sheetsas a chart recording or scope photo. Short-term drift differs from noise only in theunits of measure; both are small, un-predictable, and random.

Long-term drift. Slow changes in voltage -reference output that occur over min-utes, days, or months of continuous op-eration. Long-term drift, usually ex-pressed in ppm/1000 hours, is a form ofnoise and is therefore random and un-predictable.

Ageing. A gradual change in output volt-age caused by long-term changes in thecharacteristics of the reference. Ageingdiffers from long-term drift, however: itresults in a slow unidirectional changein the reference voltage, whereas long-term drift causes random fluctuations.

Noise. Electrical noise at the output ter-minals of a voltage reference. It may in-clude wideband thermal noise, low -fre-quency spikes of wideband (popcorn)noise, and narrow -band 1/f noise.Thermal noise is small and easily fil-tered with a simple RC network, unlessthe application prohibits that approach.For applications that power the refer-ence for short intervals only, most formsof noise translate to a component of theinitial accuracy.

Temperature drift. A change in outputvoltage caused by temperature, ex-pressed in ppm °C-1 or % °C-1. Usuallythe second most important specificationafter initial accuracy, it becomes domi-nant for applications in which the ini-

1.240

29mV/100` C=236ppm1°C

1.235

ACTUAL ERROR

1.230

11.225

1.220-50 -25 0 25 50 75 100 125


Fig. 3. The slope method of depictingUout vs temperature simply illustrates

the maximum dv/dtwith a straight lineon the graph.

1.240

1.235

1.230

ACTUAL ERROR

1.225 3mV FROM -40°C TO +85`C

1.220-50 -25 0 25 50 75 100 125


Fig. 4. The box method, which enclosesthe extremes of Uout variation within a

box, gives a closer approximationto the actual error.

1.240

1.235

1.230

1.225

50

ACTUAL ERROR

±1001.ATC

1.220-50 -25 0 25 50 75 100 125


Fig. 5. The butterfly method gives oneactual data point at +25 °C, plus a

limiting envelope that specifies theerror more tightly than does

the slope method.

tial accuracy can be compensated by acalibration of adjustable gain. Threemethods of specification are common.Slope method (Fig. 3): a line represent-ing the worst -case (highest) dv/dt overthe temperature range of interest. Usedmostly on older military products withan assumption that the drift is linear

(often wrong), this method enables worst -case calculations. One problem: the ac-tual point of maximum slope is not spec-ified.Box method (Fig. 4): a box formed bymin/max limits for output voltage overthe temperature rnage of interest. Thisconstruction corresponds to the methodof test, and provides a closer estimate ofactual error than does the slope method.The box guarantees limits for the tem-perature error, but (like the slope) saysnothing about the exact shape and slopeof the output response.Butterfly method (Fig. 5): a more de-tailed set of limits that actually showsone datum point (at 25 °C), with mini-mum and maximum slope lines passingthrough it, and two or more breakpointsalong each line. The name comes fromthe shape of these lines as they appearon the graph of output voltage vs tem-perature.Figures 3-5 represent the same fictitiousvoltage reference. Note that the numer-ical error estimates listed on each figureare not easily compared, but the box maybe inverted by drawing a diagonal acrossit. That slope then allows a closer com-parison with the other two methods ofspecification.

Self -heating. A change in temperatureand consequent change in output volt-age caused by the flow of load currentinternal to the reference. This effect issneaky because it has several time con-stants ranging from microseconds to sec-onds. Self -heating is rarely specified be-cause it does not appear in high-speedmeasurements of line and load regula-tion.You can choose a reference that is spec-ified at the extremes of load current, oreliminate self -heating by adding an ex-ternal transistor or buffer amplifier tohandle the load current. The monolithic,1 ppm MAX676-MAX678 referencesoffer another option: they include activecircuitry that maintains a constant in-ternal power dissipation as the load cur-rent changes.

Load regulation. An error produced by achange in load current. Like line regu-lation, this d.c. specification does not in-clude the effects of load transients.

Line regulation. An error produced by achange in the input voltage. This d.c.specification does not include the effectsof ripple voltage or line transients. Forbattery -powered applications, the mod-ern voltage reference is far superior toits predecessors, both for line regulationand for the closely related specificationof dropout voltage (associated with theminimum -allowed input voltage).

Dropout voltage. The minimum input -to -output voltage difference (also calledminimum input -to -output differential)that will guarantee proper operation.Dropout voltage sometimes appears asa line in the specification table, but itoften appears only as the lower voltage


SELECTING VOLTAGE REFERENCES La

Two -terminal andthree -terminalmicropower references

Two -terminal and three -terminal refer-ence types can differ considerably m actualpower consumption. Consider two circuits,each generating 2.5 V from a 6 V batterythat is allowed to discharge to 3 V (seeFig. C).

Quiescent current for the three -termi-nal device is the sum of the /Q shown in thedata sheet plus the load current; this sumis fairly constant over the entire range ofbattery voltage But for the two -terminaldesign, current is limited mainly by Rin, whosevalue is established by the mmunum val-ues for battery voltage (Vbattumn)) and qui-escent current (.4m.))

= Vbattinunl- Vref/ aQ(ann)

For Vbaturnin = 3 V and kemin)= 10 fA,

Ri, (3 V - 2.5 V)/ (10 fA + 100 fA)

= 4545 a

Over the battery's 3-6 V range,

/bat = (Vbatt Vref) Rui

=110 fA for Vbcitt = 3 V,

= 770 fA for Vbatt 6 V.and

Thus, the quiescent current can increasesix -fold when you install a fresh battery.

C THREE -TERMINAL REGULATOR

VBATT

63V

Er°MAX872

VREF

2 50V

6

RLOAD

110 =0µ1A

10 + ILOAD ILOAD =

= 110uA 100µA

TWO -TERMINAL REGULATOR

VBATT

6 3V +

REFERENCEDIODE

VREF =

2 50V

10µA < IQ < 20mA

10 + !LOAD =

110 TO 770uA!LOAD =

100pA940122 18

Values of R in less than 4545 S2 draw muchmore current. If, for example, you let thebattery discharge to 2.7 V instead of 3 V,R10 becomes 1818 CI and the battery cur-rent (at 6 V) becomes 1.925 mA. Powerconsumption for that condition is 11.55 mW,which is no longer micropower!

level in the conditions for the line -regu-lation specification. The dropout speci-fication is particularly important for4.096 V references powered from 5 V sup-plies.

Transient response is the response of avoltage -reference output to a transientof input voltage or output current.Voltage references are not power sup-plies, and they rarely excel in the rejec-tion of transients. Data sheets may pub-lish scope photos or typical curves fortransient and a.c. performance, but guar-anteed specifications are rare. In gen-eral, you must add other circuitry toshield the reference from line and loadtransients.

This review of reference types and specifi-cations provides most of the informationyou will need to select a reference for yourapplication. Also helpful are the followingdiscussions on countering the effects of tem-perature, a collection of pitfalls to avoid,and another collection of hints on how toenhance the performance of your voltagereference.

Circuit pitfalls

No matter how good a reference is, poor cir-cuit engineering can make it look bad. Thefollowing is a summary of the problems mostoften encountered.Ground. Noise or offset voltage in the

ground node makes all other trou-bleshooting measurements suspect. Allmeasurements should be referred to thesame point, which is connected to theKelvin ground sense pin of the reference.

Noise and glitches. Use an oscilloscopeto ensure that the reference output isstable. As with opamps, very high ca-pacitive loads may cause oscillations.When monitored with a digital volt-meter, a reference output with HF os-cillations appears to have very poor ini-tial accuracy and poor stability. Also usethe oscilloscope to look for transients onthe reference output caused by rapidlyvarying load currents, such as thosedrawn by the reference inputs of someA/D converters.

AID converters. These devices, particu-larly successive -approximation types,have high-speed switches that may in-troduce extremely narrow, energetic cur-rent pulses at the source and referenceinputs. You may have to buffer the ref-erence with an amplifier or a resistor of

20-100 SI. Contrary to intuition, addingcapacitance to ground can make thingsworse.

Buffering. The initial offset voltage, off-set -voltage temperature drift, and gainerrors of most buffers will significantlydegrade the reference accuracy if yousimply connect a buffer to the referenceoutput. The preferred method is to in-clude the buffer inside the reference'sfeedback loop (via its sense inputs).

Temperature. Many references include aPTAT (Proportional To Absolute Tem-perature) output for convenience, so youneed only add (for instance) an opampdriving a power transistor in close ther-mal contact with the reference. As an al-ternative in battery -powered applica-tions with a human operator, the PTATvoltage might drive a comparator thatactuates a front -panel display, warningthat the results may be out of range.

Line regulation. By filtering and pre -reg-ulating the input voltage, a zener orthree -terminal regulator can greatly im-prove line regulation, line -transient re-jection and ripple rejection. On the otherhand, most references provide only a fewmA, so a simple, low-cost RC output fil-ter may be appropriate.

Noise. Adding a simple RC lowpass filtercan reduce output noise, but the capac-itor should have very low ESR to be ef-fective at the audio frequencies. Checkthe reference data sheet before addingcapacitance to the output-too much ca-pacitance may cause oscillation.

Source and sink capability. An externalbuffer amplifier can deliver more loadcurrent, but be sure to use a referencewith separate force and sense terminals,which is designed to drive an externalpass transistor within the reference'sfeedback loop.

Design exampleA simple battery -powered adaptor (seeFig. 6) converts an ordinary DVM into a4 -wire milliohmmeter that accurately mea-sures the resistance of wiring, motor coils,solenoids,high-current inductors, and metershunts. It can quickly locate short-circuitsin a power supply or on a printed -circuitboard. The circuit shown is about 2% ac-curate. For higher accuracy, you can makecomponent adustments as described below.

The circuit applies 1 A, 100 mA, or 10 mA,according to to the range switch setting, tothe unknown resistance via two test leads.You then set a DVM to the 2 V range andconnect it with two more test leads, form-ing a 4 -wire connection to the resistancebeing measured.

The DVM indicates directly in ohmswhen you depress the momentary -on powerswitch, S1. A 100052 resistance, for instance,reads 1.000 Von the circuit's 1 A range, so1 mV corresponds to 1 ma Four -digit andfive -digit DVMs frequently have 1 pV sen-sitivity, providing resolutions of 1 paBecause the output is a current source, the


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unknown resistance of the connections andtest leads is not a source of measurementerror.

Accuracy depends on the DVM, theop amp's input offset voltage (±70 p.11 max),and the tolerance of R1, R2, R4, R5, and R6.First, trim the 1 A range by selecting R4 orby adding a trimming potentiometer be-tween RI and R2. Next, trim the 100 mArange and then the 10 mA range by ad-justing the highest -valued resistors in theR5 and R6 networks.

Depressing Si turns on the micropowerreference, IC1, which produces 2.500 V.Resistors R1 and R2 divide that output to0.1 V, and the op amp forces 0.1 V at thesource of Ti. This action creates a currentsource that develops 0.1 V across R4, R5 andR6. The range switch selects a current of1 A, 100 mA or 10 mA in the loop formedby the resistors, the unknown resistance,the 1.5 V battery, and T1.

Note that releasing Si (or disconnectingthe adaptor) eliminates all current drainfrom the 1.5 V battery. An alkaline D celltherefore produces thousands of measure-ments, even on the 1 A range, if you depressSi for brief readings on the DVM only. The9 V battery can last for years because itsload is smaller than 30 pA.

To search for a short-circuited compo-nent or a short between tracks on a PCB,first connect the two adaptor leads, one toeach of the relevant tracks. Connect a DVM

lead to the same point as one adaptor lead,and use the other DVM lead to probe alongthe tracks. The highest reading on one trackand the lowest reading on the other trackreveal the location of the short-circuit.

Constant readings indicate no adaptor cur-rent flowing in that section of the track (fora given connection of the adaptor leads), soyou can eliminate that section from thesearch. 19401221

S2 :1 : 1A (1m(1/mV)2 : 100mA (10mO/mV)3 : 10mA (100m52/mV) 940122-19

Fig. 6. Operating with a DVM, this low -power adaptor circuit performs4 -wire, low -resistance measurements.


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NEW BOOKSA Beginners Guide to the Microchip PICBy Nigel C. Gardner, Bluebird Electronics100 pages; disk included.Price: £19.95

This little book covers roughly the samegrounds as the PIC programming coursefeatured in four instalments in ElektorElectronics last year, although it must benoted that its entrance level is much lower.The title of Mr. Gardner's book is, there-fore, fully appropriate, because the BeginnersGuide' is excellent for those who havenever worked with Microchip Technologies'PIC series of RISC microcontrollers.

The book lays a solid base by first dis-cussing elementary concepts such as ASCIIand hexadecimal notation, file formatsand product development, before dis-cussing the internal structure of the PIC.Then comes the interesting bit: hardwareinterfacing and programming. A good dis-cussion is presented on the choice of os-cillators for the PIC, which is an importantsetting before any programming can be done.

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Hands-on Guide to OscilloscopesBy Barry RossISBN 0 07 707818 7Price £17.95 (soft cover)All oscilloscope users, from students andhobbyists to experienced engineers and de-signers, will find this guide to oscilloscopesinvaluable. The book covers all aspects ofoscilloscope use. Assuming a minimum ofprevious knowledge, the book is devel-oped to allow the novice to become famil-iar with oscilloscope circuitry and the cor-rect operation of the instrument in a widerange of applications. It explains morecomplex oscilloscope functions such asdigital storage circuitry and the correct useof digital storage oscilloscopes (DSOs).Coverage includes complete chapters onprobes and their use, choosing oscillo-scopes and what to do when things gowrong. Practical application examples atthe end of each chapter develop the pos-sible uses of the oscilloscope with a min-imum of extra equipment. It is this prac-tical and comprehensive approach whichshould ensure that the text finds a broadreadership among engineers, scientists

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Build your ownElectronic Test Instruments

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Build your own

Short course 8051/8032Microcon-trollers and assemblerThis book presents a course whichdescribes the hardware and thesoftware to make a completemicrocontroller system. The controllerused is selected from the MCS-51family produced by Intel and others.

142 pages; illustrated;230x120 mmISBN 0 905705 38 6Price: £ 9.95 ($ 18.50)

SMT ProjectsThis book describes the specialfeatures of surface mount technologyand how to work with surface mountdevices on the workbench. It includesover 20 construction projects, all ofwhich have many practicalapplications in and around the homeand workshop.

174 pages; illustrated;210x140 mmISBN 0 905705 35 1Price £ 9.95 ($ 18.50)

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For testing and inspecting electrical and electronicequipment a multitude of electronic test instruments isrequired. Most of these instruments are, of course,commercially available. However, for all kinds of reason(cost, challenge, for instance) many reserachers,enthusiasts and experimenters like to build suchinstruments themselves.This book will help them: it contains detailed designs for17 measuring instruments, seven generators andanalysers, ten miscellaneous instruments and a numberof ancillary and auxiliary circuits.

The designs range from a simple multicore tester to asophisticated logic analyser. Most of the designs containa special printed circuit (or circuits), full-scale drawings ofwhich (with some exceptions) are given in an appendix tofacilitate the photographing and subsequent production ofthe boards.Beginners in electronics will find the first chapter, dealingwith measurement techniques, a good introduction to thefascinating world of electronic test and measurement.

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305CIRCUITS

DATA BOOK 5APPLICATION NOTES

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Databook 5: Application NotesThis book contains a large number ofcollected Application Notespublished by well-known European,American and Japanese chipmanufacturers. The notes cover bothanalogue and digital circuits and forma rich source of inspiration for allelectronic designers.

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44

D efore we go on to examine1.)digital circuits in detail,we will run briefly throughsome of the essential back-ground to an understanding ofdigital electronics. Last monthwe explained the binary basisof digital circuits and howfacts and numbers can be rep-resented in them. We also de-scribed the three fundamentallogic operators: NOT, AND andOR.

Circuits can be built to per-form the function of a logic op-erator. Such a circuit is knownas a logic gate. A gate has oneor more inputs, but only oneoutput. It is possible to assem-ble gates from discrete compo-nents, such as transistors,diodes and resistors, but thisis rarely done. Almost invari-ably we use an integrated cir-cuit that provides one or (usu-ally) more gates. Figure 5

11

7404

7

DOT OR NOTCH TOINDICATE PIN 1

A

NOT

940120 - II - 15

Fig. 5.

shows a typical logic IC: thesymbols drawn within the out-line show the pin connectionsof the six identical gates it con-tains. Each gate performs theNOT operation. Two pins pro-vide the power connections to

THE DIGITAL SOLUTIONPart 2 Digital essentials

By Owen Bishop

In this series we look closely at digital electronics,what it is, what it does, how it works, and its

promise for the future.

all six gates. Each gate hasone input and one output. Thesymbol used in logic diagramsfor a NOT gate is a rectanglewith a figure 1 inside and ashort slanting stroke at theoutput. It is the slantingstroke that indicates the in-verse nature of the output.

A NOT gate may be in one oftwo states:

Um high Uout lowUin low Uout high.

The output is the inverse (orcomplement) of the input. Ifwe take a high input or outputto represent 'true', a low inputor output represents 'false' or'NOT true'. Very occasionallywe use so-called negative logic,in which true is represented bya low voltage and false is rep-resented by a high voltage.

The behaviour of a gate issummed up in a truth table.This is a table that lists all thepossible states of the input (orinputs, if more than one) andthe corresponding states of theoutput. For a NOT gate, thetruth table is

InputA0

1

Output

1

0

An AND gate has at least twoinputs. The output is high onlywhen both (or all) inputs arehigh. If any one, or more, ofthe inputs is low, the outputgoes low. The truth table forAND summarizes the opera -

AND

AZ= AB

E3 &

A

C

Z = ABC

940120 -II- 16

OR

= A.B B .A1-13.rCC

940120 -11- 17

tion:

InputsA B

Output

0 0 0

0 1 0

1 0 0

1 1

Note that the four lines of thetable cover all four possiblecombinations of states of thetwo inputs. A three -input ANDgate has this truth table:

AInputs

B COutput

0 0 0 0

0 0 1

o 1 0o 1 1

1 0 01 0 1

1 1 01 1 1 1

Z is true only when A AND BAND C are true. Once again wehave covered all possible com-binations of inputs. Note thatthe way to ensure that all pos-sibilities are listed is to fillcolumns A to C with the binarynumbers equivalent to 0 to 7.Figure 6 shows the commonlyused symbols for 2 -input and3 -input AND gates.

A high input on any one ormore inputs of an OR gategives a high output. The truthtable for a 2 -input NOR gate is:

InputsA

Output

0 0 0

0 1 1

1 0 1

1 1 1

Compare this with the truthtable for an AND gate. Figure7 shows the symbols for the2 -input and 3 -input OR gates.

Although OR, AND, and NOTgates are able to cover all pos-sible logic operations, a partic-ular circuit may require alarge number of such gates.Simplification and reduction ingate numbers is made possibleby the use of certain othertypes of gate.

Figure 8 shows the symbolfor a NAND gate. As the symbolimplies, this is an AND gatewith a negated output. Its logicequivalent in terms of AND andNOT is shown in Fig. 8b. Itsname is a contraction ofNOT -AND. Note that the nega-tion of AB (or NOT -AB) is indi-cated by a bar over AB to giveAB. Here is the truth table fora 2 -input NAND gate:

InputsA

Output

0 0 1

0 1 1

1 0 1

1 1 0

Corresponding to NAND, thereis also a NOR, or NOT -OR gate(see Fig. 9). Its truth table is:

InputsA B

Output

0 0 1

0 1 01 0 0

1 1 0

A variation of OR logic is

NANDA

-1_

ANDA

AB&

Z =AB

NOT

tS.-

940120 -11- 18

NORA I-

N --

OR NOTA

AA+B +B

B

940120 -11- 19

Fig. 6. Fig. 7. Fig. 8. Fig. 9.


THE DIGITAL SOLUTION - PART 2 45

known as exclusive OR or XOR.

It applies only to a 2 -inputgate. The output of an OR gateis high if one input or the otheror both inputs are high. Theoutput of an XOR gate is high ifone input or the other, but NOTboth, is high. This is shown inthe truth table:

InputsA B0 0

Outputz

0 1 1

1 0 1

1 1 0

A 2 = A + BB =1

exclusive - OR

A sZ-= A + Be =1

exclusive - NOR940120 -11 - 20

Fig. 10.

There is also an exclusive -NOTgate whose output is the in-verse of an XOR gate. TheXNOR gate is also known as theparity gate or coincidence gate,since its output is high whenboth inputs are low or both arehigh. The symbols for XOR andXNOR gates are shown inFig. 10.

All logic operations can beperformed with only NANDgates or only NOR gates as willbe explained later.

Logic familiesThere are several ways of im-plementing a gate as an inte-grated circuit. Manufacturershave produced several familiesof ICs that comprise not only

OUTPUT Z

940120 - 11 - 21

Fig. 11.

individual logic gates but alsomore complicated logic circuitsconsisting of several or manysuch gates connected togetheron a single chip. The morecomplex logic devices includecounters, dividers, coders anddecoders, registers, and arith-metric units. The most com-plex of all include microproces-sors, memories, modems andmany other specialized logicdevices. A family of logic ICs isbased on one particularmethod of fabrication. One ofthe most successful and widelyused of these is transistor -transistor logic, abbreviated toTTL. The circuit of a gate isbased on a number of n -p -nbipolar transistors plus a fewresistors and diodes. The ICsof this series all have a typenumber beginning with 74.This is followed by two or moredigits to indicate the device ordevices in the IC. For example,7400 has four 2 -input NANDgates; 7404 has six NOT gates;74151 is a more complex IC, an8 -bit multiplexer or data selec-tor.

The 74 series is used lessoften nowadays, since it hasbeen superseded by severalvariants, identified by code let-ters in the type number. Theperformance of these sub -fami-lies is superior to that of theoriginal 74 series in variousways. Thus, the 74LS seriesrequires less power. The 74HCseries is based on complemen-tary MOS transistors; itspower requirement is verysmall and it has a wider rangeof operating voltages. In par-ticular, it can operate on volt-ages as low as 2 V, making itvery suitable for battery -pow-ered equipment. The 74AC se-ries is able to operate at higherspeed than the other series. Allseries have equivalent ICs; forexample, the 74LS00, 74HC00and 74AC00 all have four2 -input NAND gates with iden-tical pin connections.

Another major series is the4000 series. This has ICs thatare equivalent to the 7400 se-ries. For example, the 4011,with four 2 -input NAND gates,is the equivalent of the 7400,though the pin connections areslightly different. The 4000 se-ries has a wide range of oper-ating voltages (3-15 V), but isappreciably slower than the7400 series and its relatives.But it is fast enough for manypurposes.

A

1

A - -1e7

~ABAB

A1

\ A

A

=A 13 = A+B

IZA,+ B

940120 -11 - 22

Fig. 12.

Emitter -coupled logic (ECL)is one of the fastest families.Its speed is due to the bipolartransistors not being switchedfully on. This means that theyare not saturated and it takesfar less time to switch them offagain. The disadvantage isthat high and low levels areclose and ECL is relativelymore subject to noise.

Integrated injection logic(I2L) has a very simple con-struction (see Fig. 11), with noon -chip resistors. This resultsin considerable saving ofspace, so making I2L particu-larly suitable for buildinghighly complex circuits on asingle chip. In the NAND gateof Fig. 11, a low input to eitherone or both of the input termi-nals draws current throughthe p -n -p transistor and turnsthe n -p -n transistor off. Thisgives a high -impedance out-put, that is, one which drawsno current from the input of an

I2L gate connected to it. If bothinputs are high, current flowsto the base of the n -p -n tran-sistor, turning it on. The out-put will now draw currentfrom another gate input, so itacts as a low -impedance out-put. The demand for fast low -power ICs for use in battery -powered equipment such aslap -top computers has led tothe development of low -voltageCMOS ICs. Series such asLV-HCMOS and HLL operateon 3.3 V.

Logic operationsIt was stated earlier that alllogic operations can be per-formed with nothing but NANDgates or NOR gates. Figure 12shows how the basic opera-tions may be performed. InFig. 12a the inputs of theNAND gate are wired together,so they are both high or bothlow. Examination of the truth

(a) AND gate (b) OR gate (c) NOT gate

1 AB = BA A+B = B+A2 (AB)C = A(BC) (A+B)+C

= A+(B+C)3 AA=A A+A = A4 A 1 = A A+1 = 15 AO = 0 A+0 = A6 A(B+C) AB+AC7 AA=O A+A = 18 A=A

Box 3. The eight theorems derived from the basic rulesof Boolean Algebra.


46 GENERAL INTEREST

table for NAND shows that onlythe first and last lines apply,giving the same table as thatfor NOT. In Fig. 12b, we usethis action to invert the actionof a NAND gate and so obtainAND.

The action of the circuit ofFig. 12c is best followed byusing a truth table. We usethis as an example of the tech-niques used for symbolizinglogic operations.

AB A B KTIAB0 0 1 1 1 0

0 1 1 0 0 1

1 0 0 1 0 1

1 1 0 0 0 1

Begin by filling in all possiblecombinations of inputs in thefirst pair of columns. In thesecond pair of columns, wehave the outputs of the NOTgates, which consist of the in-verse of their inputs. Thatthese are inverses is indicatedby the bar over each symbol.In the column headed A B, wehave the effect of ANDing Aand T3. (check with the truthtable for AND that values areentered correctly). This is thefirst stage of the NAND opera-tion. To symbolize the AND op-eration, it is conventional towrite the symbols A and B sideby side with no gap betweenthem, just as when we write abin algebra to indicate multiply-ing a by b. In the last columnwe have the inverse of A B,written A B. This completesthe NAND operation. Compa-ring the last column with thetruth table for OR, we see thatthey are identical: NANDingthe inverses of A and B is thesame as ORing them.

Figure 12d shows how tobuild an XOR gate from NANDgates. The truth table is:

A B AB A(AB) B(AB) ACE0 0 1 1 1 00 1 1 1 0 1

1 0 1 0 1 1

1 1 0 1 1 0

Use the table for NAND to workout the steps in the tableabove. In the last column wewrite the NAND of the two pre-vious columns. Comparisonwith the table for XOR showsthat these four NAND gatesperform the function of XOR.The last column is headed withA and B joined by the symbolfor XOR. The symbol for XOR isCD and that for XNOR is 0.

These few examples show thatelectronic circuits are able toperform a range of logic opera-tions from the simplest to themost complex.

Boolean algebraIt is clear from the precedingsection that there is more thanone way to effect a logic opera-tion. One of the aims of logiccircuit design is to reduce thenumber of gates required to aminimum. Logic expressionscan be simplified according tothe rules of Boolean Algebra.The basic rules, or axioms, arethose which govern the opera-tion of NOT, AND and OR gates.From these we derive a num-ber of theorems which arelisted in Box 3. A and B arelogic variables that can takethe value 1 (high) or 0 (low). Inthe box, the symbol repre-sents AND, where writing thetwo symbols side by side wouldnot be clear. To confirm any ofthe eight theorems, draw outthe corresponding logic dia-gram and consult the appropri-ate truth tables. Theorems 1, 2and 6 can be extended to applyto a greater number of vari-ables.

Simplifying logic diagramsis a matter of using the theo-rems. Take the diagram inFig. 13 as an example. Startby labelling the inputs A, Band C. Work from left to right,writing the output valuesagainst each gate and carryingthese values on to the nextgate. The result is the equa-tion:

Z = AB(B+AC).

Removing the brackets (Theo-rem 6a):

Z = ABB+ABAC.

But BB = B (Theorem 3a), and

AA = 0 (Theorem 7a):

Z = AB+0BC.

From Theorem 5a:

Z = AB+0.

From Theorem 5b:

Z = AB.

Thus, the circuit of five gatessimplifies to just one AND gate.Also, the result shows that thevalue of Z does not depend onthe value of C. Not all circuitswill reduce so dramatically,but it is usually possible tomake at least a small reduc-tion in the number of gates.One useful technique for ana-lysing and then simplifyinglogic statements is a KarnaughMap. This is really a differentway of setting out the truthtable for the number of vari-ables involved, followed by aroutine for simplifying the ex-pressions and for identifyingredundant variables (such as Cin the example above). For de-tails of the Karnaugh tech-nique, the reader is referred toone of the standard textbookson Boolean algebra.

Digital mathsElectronic circuits can handlelogic and, since maths has avery logical basis, they have nodifficulty in handling numeri-cal operations, too. The onlycondition is that the numbersmust be expressed in the bi-nary system. Let us look at bi-nary addition. The rules foradding two binary digits are

0+0 = 00+1 = 11+0 = 11+1 = 1, carry 1.

Ignoring the carry for the mo-

AC

=1

AB

Z = AB(B+1C)

940124 -11- 23

Fig. 13.

ment, we can set out the digitsto be added (A and B) andtheir sum (Z) in a table:

A B Z

0 0 0

0 1 1

1 0 1

1 1 0

This is recognizable at a glanceas the truth table for XOR. Onestage, at least, of binary addi-tion can be done with one ofthe logic gates we have alreadydescribed. The table for thecarry digit, Z', is:

A B Z'0 0 0

0 1 0

1 0 0

1 1

This is the truth table for AND.Since we need an AND gate forthe carry digit, we do not needan XOR gate as such; the com-bination of AND and two NORsin Fig. 14 performs the XORfunction. This circuit is knownas a half -adder, because its op-eration is restricted to addingtwo one -digit binary numbers.

Sometimes, this is all thatis required, but more often wewant to add two numberswhich each have several digits.For this operation we need acircuit that is able to acceptthe carry -in digit from a previ-ous stage of addition. Figure15 shows the circuit of a full -adder, which has an input forthe carry -in digit. Its outputsare Z (the sum of A, B, and thecarry -in digit), and a carry -out,Z', to the next stage.

To add two binary numbersof n digits each, we need ahalf -adder for the first digitand (n-1) full -adders for theother digits (Fig. 16). Such acircuit is able to add all thedigits of the two numbers si-multaneously and is known as

(carry out)

940124 -11- 24

Fig. 14.


THE DIGITAL SOLUTION - PART 2 47

a parallel adder. In practice,addition is not completely si-multaneous, for it takes timefor each stage to produce thecarry digit and pass it on tothe next stage. The carryprocess ripples along the chainof adders and, until carryinghas reached the last adder ofthe chain, the output will beincorrect. This ripple effect issomething that has to betaken account of in the designof digital circuits.

Binary subtractionIt is possible to design logiccircuits to subtract one binarynumber from another, butthere is no need to go to suchlengths. With a little manipu-lation of the digits, we canarrange for them to be sub-tracted by using an additioncircuit. There are two meth-ods, the first of which uses thel's complement. This is ob-tained by writing (or obtain-ing by a NOT gate) the inverseof each digit of the number tobe subtracted. For example,find

100101-11001.The l's complement of 11001is 00110

Add 100101Sum 101011

Remove the digit from the leftof the sum and add it to theremainder

Result

010111

1100

This technique is easily per-formed by logic circuits or acomputer program. Anothertechnique uses the 2's comple-ment. This is obtained by tak-ing the l's complement andadditing 1 to it. In the exam-ple above, the 2's complementof 11001 is

00110Add 1

Gives 00111Add 100101Sum 101100

Remove the digit from the leftand discard it; the result is01100 = 1100 since the 0 atthe left can be ignored. Mostcomputers use the 2's comple-ment.

Negative numbersSometimes we use a specialconvention for expressing neg-ative numbers. The first digit(or binary digit or bit) is usedas a sign bit. If this is 0, thenumber is positive; if it is 1,the number is negative. Therest of the number representsits magnitude. If the sign bitis 0 (positive number), the re-maining bit represents themagnitude in the usual way. Ifthe sign bit is 1 (negativenumber), the remaining bitsrepresent the l's complementor the 2's complement. Usingthis system, we add the signbits along with the rest of thenumbers so the same logic cir-cuit is used, whether or notthe sign bit convention isused. If two positive numbersare added, the result is thesame in either case. If one orboth are negative, we need totake the convention into ac-count when interpreting theresult. In the example above,which may be rewritten as100101+(-11001), write thenumbers according to the signbit convention, noting thatboth numbers must have thesame number of digits:+100101 is written 0100101;-11001 is first written as-011001 to give it the samenumber of digits, then takesits complement. The 2's com-plement is 100101+1 =

100111. Precede by the nega-

CARRY IN

>1 >1

\ Z(carry out)

940124 - II - 25

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A range of Printed Circuit Boards in stock from many of the Projects in MagazinesPRACTICAL WIRELESS 0 SHORT WAVE MAGAZINE U ELMO:ORLI HRT

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IF ANADVERT IS WRONG,

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tive sign bit to obtain 1100111and add the two numbers:

01001011100111

Sum 10001100As usual in 2's complementarithmetic, discard the firstdigit to give 0001100. This be-gins with a 0, so it is positivewith a value 001100 = 1100.

Subtracting the first num-ber from the second:11001+(-100101) gives a nega-

tive result: write 11001 as0011001, including the signbit and 100101 as its 2's com-plement, preceded by its nega-tive sign bit: 1011011. Thus

00110011011011

gives 1110100.The first digit shows that theresult is negative. The 2'scomplement of the remainderis 001011+1 = 001100 = 1100.

Next month we shall see howthis outline of essentials is ap-plied in practice.

A,HALF

ADDER

C -OUT

Test yourself1. Show by writing out the

truth table that inverting Aand B and then ORing themis equivalent to ANDingthem.

2. Check that the circuit ofFig. 14 adds correctly bywriting out its truth tables.

3. Find:(a) 11001011+1001101;(b)10101010-111101.

AlC IN

FULLADDER

C -OUT

A2C IN

FULLADDER

C -OUT

Answers toC IN

3

FULL Test yourself (1)ADDER

1. a) 10011; b) 101101;C -OUT c) 10100111.

A,B,

A3 A2 Al+ 132 B,

Z4 2. a) 12; b) 39; c) 2897.

- II - 263. a) 16; b) 5F; c) CD7.=Z4 Z3 Z2 Z, Zo 9401204. 011010000010.5. 951.

Fig. 15.


Fig. 16. [940124 -ID


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all modes inc HI PIES monochrome. Complete with 'text'switching for WP use.(possibte minor screen bums) Syncs down to 15kHz. Supplied in EXCELLENT little used condition with full 90 day guar-antee.Order as faS-9600 / H for ATARI £159.00 (E)Ail modes as above Order as MTS-96001 S £139.00 (E)ELECTROHOME ECM-1211SBU 12" VGA multisync monitor withresolution 640 x 480. Multi input selection; 9pin CGA/ EGA ; 15 pinVGA or 5 BNC connectors. 0.31 pitch. Compatible with PCs, Amiga,Atari and others. In good used condition (possible minor screenbums). 90 day guarantee. £99.00 (E)KME 10" high definition colour monitors. Nice tight 0.28" dot pitchfor superb clarity and modem styling. Operates from,-,any 15.625 khz sync RGB video source, with RGB:analog and composite sync such as Atari, -Commodore Amiga, Acorn Archimedes & BBC.Measures only 13.5" x 12" x 11". Only £125 (E)Good used condition. 90 day guarantee.KME 10" as above for PC EGA standard £145.00 (E)

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Laser VideoOne of the most amazing surplus deals Disk Playerthat we ever been able to offer you!The Philips VP410 LaserVision player, in as new condition, unit fea-tures full computer control, Plays standard 12" LaserVision disks withstartling visual and audio quality in two channel stereo or mono.When controlled by a computer, it may also be used as a versatilehigh quality storage / retrieval medium. It will play back eitherLaserVision CAV (active play) or CLV (Long Play) discs (which cov-ers most types of commercially available video discs). Some of themany features of this incredible machine are:RS -232 INTERFACE RGB COMPOSITE VIDEO OUTPUTBNC+SCART INTERFACE PAL/ RGB DECODERIR+WIRED REMOTE CONTROL FAST RANDOM ACCESS

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Ifi

QUASI -ANALOGUE CLOCKWORKDigital watches with displays consisting of numbers only havelost much of their popularity over the last few years. They arenow outnumbered by traditional dials with hour and minutehands actuated by a digitally controlled stepper motor. Thesewatches (and clocks) are the best of both worlds because theyhave an analogue readout with digital control. The LED clockdescribed in this article is based on the same principle, onlythere are no moving parts at all.

9

Design by P. Hogenkamp

'VFW quasi -analogue clockwork dis-1 cussed in this article uses144 LEDs (light emitting diodes) to in-dicate the time on a round, quasi -ana-logue dial with a diameter of about22cm. One of twelve green LEDs lightsat maximum intensity to mark thehours, while the other eleven aredimmed. Between two green LEDs sit11 red LEDs, each of which representsa period of five minutes. In this way,the time is indicated with an accuracyof five minutes. This would seem to beenough in view of the mostly decora-tive function of the present clockwork.

To keep the circuit as simple as pos-sible, it is based on discrete logic inte-grated circuits from the 4000 CMOSseries only.

Circuit description

The complete circuit diagram of theclockwork is given in Fig. 1. The powersupply is a simple, conventional, de-sign which also supplies a pulse -shaped 50 -Hz signal. These pulses arederived from the mains voltage withthe aid of a network consisting of R20and C5. Next, Schmitt -trigger IC4bturns the sine -wave shaped pulsesinto rectangular pulses which are usedto clock counter/divider IC1. Since thisIC is wired for a total divisor is 1,500,the frequency of the output signal is1/300 Hz. That equals one pulse perfive minutes. A divisor of 1,500 isachieved by detecting the binary code`1500' with the aid of IC2a and IC2b.

When the value 1500 is reached, apulse is generated via R5 and C1. Thepulse is cleaned and shaped by gatesIC3, and IC3d. Next, it resets IC1, andincreases the contents of IC5 by one.The other input of IC3d is connected topush button Si. This button serves toadjust the clock. The pulse supplied bythe push-button is `debounced' by net-work R3 -R2 -C3. Every time the buttonis pressed, the readout will advance byone LED position.

Circuit IC5 operates as a five -min-utes counter, and has 12 states, corre-sponding to 0, 5, 10, 15, 20, 25, 30,35, 40, 45, 50 and 55 minutes.Theoutputs of IC5 determine which outputof multiplexer IC7 (a 4067) is actuated.The common input of the multiplexeris connected to the +12 V supply railvia a 680-Q resistor, R1. When all mul-tiplexer inputs (A -D) are held at 0, theanode terminals of the LEDs con-nected to output AO (D1, D13, D25, D37,D49, D61, D73, D85, D97, D109, D121 andD133) are connected to the 12-V supplyvia resistor R1. To make a LED light,however, its cathode must be pulled toground. That is done by another multi-plexer, IC8, which has its common out-put connected to ground via R4(820 SI). The binary pattern applied tothe A -D inputs determines which LEDhas its cathode connected to ground.

As soon as IC5 reaches state '12'(which corresponds to 0 minutes), thecounter is reset via IC4, and IC4d. Also,IC6 receives a clock pulse which marksthe start of a new hour. Increasing thecontents of IC6 results in the next out-put of IC8 going low. The multiplexerthen ensures that the cathodes of theselected LEDs are pulled to ground. Assoon as IC6 supplies the binary code`12', a reset pulse is generated via IC3b,R7, C4 and IC3a. This pulse resets IC6to state '0', so that the counter canstart to count 12 hours again.

The structure of the LED matrixmay be a bit difficult to distill from thecircuit diagram. It is, therefore, shownseparately in Fig. 2.

As already mentioned, the displayhas 132 red LEDs and 12 green LEDs.The green LEDs light continuously atlow intensity. This is achieved by con-necting their cathodes to ground via10-kQ resistors (R8 -R19). If you want toincrease the brightness of the greenLEDs, you may lower the value of R8 -R19 to, for instance, 3.3 1(Q. Since theanodes of the LEDs are connected to+12 V via resistor R23, a constant cur-rent of about 0.5 mA flows througheach LED. At the full hour, the rele-vant green LED must light at maxi-


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mum intensity. That is achieved byconnecting a diode and an 820-52 re-sistor, R4, in parallel with the selectedLED. This trick explains why the LEDsconnected to line AO are wired differ-ently in the matrix.

The power supply of the clockworkis straightforward. A discrete bridgerectifier turns the 9-V alternating volt-age applied by a transformer into a di-rect voltage of about 12.5 V. A

Fig. 2. Schematic structure of the LED ma-trix. Note that the LEDs which indicate thehours are connected in a special way.

resistor-zener diode stabilizer, R22 -

D161, is used to obtain a reasonablystable +12 V supply voltage. LED D162is located in the centre of the dial, andlights as a soon as the supply voltageis present. The last LED on the dial,D163, flashes at a slow rate to indicatethat the clock is 'ticking'.

ConstructionThe printed circuit board designed forthe clockwork has a fairly unusual sizeand shape. The special design is nec-essary because the circuit board dou-bles as the dial of the clock. The tracklayout and component mounting plan

Fig. 3. Track layout and component mounting plan of the clockwork PCB, shown at 85% of true size (board available ready-made through the


QUASI -ANALOGUE CLOCKWORK

Resistors:Al = 6800R2 = 39016/R3,R5;R6;R7 = 82k52R8 -R19 = 10kR20 = 2200R21;R24 = 2022R22 = 100 1WR23 = lk,(15

Capacitors:C1 -05;C8 -C15 = 100nFC6;C7 = 100pF 25V

Semiconductors:D1;D13;025;D37;049;D61;D73;D85;D97;D109;D121;D133 = LED, green, 3mmD2-D12;D14-D24;026-036;D38-D48;D50-D60;D62-D72;1374-D84;D86-D96;D98-D108;0110-D120;D122-D132;D134-D144;D162;D163 = LED, red,3mmD145 -D156 = 1N4148D157 -D160 = 1N4001D161 = 12V 1W zener diodeIC1 = 4060IC2 = 4082

IC3;1C4 = 4093IC5;1C6 = 4024IC7;1C8 = 4067

Miscellaneous:K1;K3 = 2 -way PCB terminal block,raster 5mmK2 = 2 -way PCB terminal block, raster7.5mmS1 = Multimec 2CTL2 press keyPrinted circuit board 930024 (see page78).

Readers Services, see page 78).


56 Please mention Elektor Electronics when contacting advertisers

Use your electronics know-how tocreate great sound!Speaker Builder, the world's only loudspeaker

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A344;------.4.magazine in English, can show you how to achieve - excellence in sound from your stereo system. Li', i;Whether you're modifying and improving yourpresent speakers or building a new design fromscratch, Speaker Builder contains the latest inloudspeaker technology. Within its pages, learnabout Thiele -Small design software, build an in-expensive measurement mike good enough for theprofessionals, or simply indulge in reading aboutthe experiences of others using their technicalskills to improve the sound around them.

Since 1980, Speaker Builder has been exploringboth the traditional and more unusual formats for loudspeakers. From pipes tocorrugated boxes to transmission lines and electrostatics, every conceivablemedium is discussed. An international forum for speaker enthusiasts the worldover, sharing ideas and designs, Speaker Builder has made it possible forthousands to enjoy the highest quality sound without straining their budgets.

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are given in Fig. 3. Unfortunately, theposition of the LEDs in a circle re-quires a fair number of wire links onthe board.

The board which comes through ourReaders Services is square, and maybe made round with the aid of a jig-saw before any components are fitted.The circuit board underneath C6 andC7 has to be cut out to give these ca-pacitors a recessed mounting.

After the sawing work, start theelectronic construction by fitting thewire links. Next, all parts may bemounted. Because the clockwork willhave to be as flat as possible, it is nec-essary to mount the LEDs close to theboard surface. Also use miniature ce-ramic decoupling capacitors. If you areconfident about your soldering skills,you may fit the ICs without sockets.

The clock will start to work the mo-ment the 9-V transformer is connectedto terminal block Kl.

Assuming that the clockwork ishung up with K1 down and push-but-ton SI up, the first green LED to lightwill be DI. The time indicated is thenthree o'clock. Every time Si is pressed,the clock is advanced five minutes.

The finishing touches to the clockdepend on your own creativity. For in-stance, the dial may be covered by a

IF AN ADVERTIS WRONG,WHO PUTSIT RIGHT?

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round bezel, which partly obscures thecomponents, but leaves the activeLEDs clearly visible. Alternatively, apiece of perspex leaves the works' in

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FOCUS ON: DEBUGGING PCsT D AGNOSTIC:

This article, apart from giving some insight into the cause oferrors that can occur in a PC, presents a power -on self -test(P.O.S.T.) card which provides a number of powerful hardwarefault tracing utilities.

Design by M. Rathjen

USING a PC is one thing, getting itto work again after a major crash

is another kettle of fish. What do youdo if the machine fails to boot all of asudden, and only produces a couple ofshort beeps at power -on? That will typ-ically happen when the guarantee pe-riod has just expired, and you are hardpressed to get a report out by thedeadline.

As of the IBM PC/AT, an 80286 -based PC introduced in 1983, everyPC, be it a 386, 486 or Pentium type,has a built-in power -on self test func-tion (P.O.S.T.). In most PCs, thepower -up booting sequence is per-formed in steps, leaving certain codesat port address 80H. The meaning ofthis 'diagnostic' code may be found in

a list which is supplied (rarely, though)by the manufacturer of the BIOS (basicinput output system) ROMs in the PC.Although P.O.S.T. codes are not in-tended for the end user, they do pro-vide useful information on what goeswrong in a faulty PC during the crucialboot -up phase. After all, if the machinedoes not get past the self -testingphase, you will be unable to load andrun special diagnostic programs fromdisk.

The half-length 8 -bit insertion carddescribed here captures and indicatesthe P.O.S.T. code on a pair of 7 -seg-ment displays. It may be configured toread other port addresses as well, andalso gives a present/absent indicationof the PC's four power supply voltages.

MAIN SPECIFICATIONS

Card address:

PSU check.Display.

Card type:

user selectable, 60H,80H, 84H, 90H, 280Hor 300H.4 LEDshexadecimal, 2 -digit7 -segment LED8 -bit, ISA, through -plated

General points

Immediately after the PC is switchedon, some pretty rigorous testing isdone on the internal hardware. TheBIOS integrates a number of routineswhich check out nearly everything in-side the PC, from the memory to theinterrupt (IRQ) routines. Before eachtest, the BIOS sends the correspond-ing P.O.S.T. code to the diagnosticport. If the PC remains 'stuck' in a cer-tain test routine, the associatedP.O.S.T. code will remain on the dis-play, allowing you to start thinkingabout a possible cause of the problem.

Let us take an example: an AT/386machine fitted with an AMI BIOS v.2.21 crashes at P.O.S.T. code 27H.According to the information inTable 1 (overleaf) this code means thatan error has occurred in the 64-Kbytebase memory test. Quite likely, thefault is in one of the memory chips, orin a SIPP or SIMM module.

The appendices with this articleshow the P.O.S.T. codes for a numberof popular BIOS ROMs. Unfortunately,owing to space restrictions, the infor-mation is not exhaustive. If your PChas a BIOS which is not listed, contactthe manufacturer to obtain a copy ofthe P.O.S.T. code set.

The electronicsIn view of the simplicity of the P.O.S.T.insertion card, a block diagram is notgiven. So, let us move on straight awayto the circuit diagram, which is pre-sented in Fig. 1. A pair of GALs(generic array logic) simplifies the cir-cuit considerably because these ICscontain a fair number of logic circuits.GAL ICI functions as the card address


P.O.S.T. DIAGNOSTIC CARD 59

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Fig. 1. Circuit diagram of the P.O.S.T. diagnostic card. Simple and effective as a stethoscope! The use of two GALs results in a remarkably lowcomponent count.

decoder. It also reads the address seton a 5 -way DIP switch. This is neces-sary because PC manufacturers unfor-tunately have not agreed on astandard address. The address settingwill be reverted to further on. The ad-vantage of a GAL over the ubiquitous'688 address decoder is that it is capa-ble of instantaneous address compari-son, i.e., not incremental -binary.

GAL ICI performs Boolean logicusing address lines AO and A9, pluscontrol lines AEN (address enable) andIOWR (input/output write) as inputvariables. It also reads the logic levels

supplied by DIL switch S1. The defaultport address setting is 60H (yes, forXTs), since that is not listed as one ofthe possibilities in Fig. 1. Remember,we are dealing with hexadecimal num-bers here. For example, address 300His selected if both A8 and A9 are logichigh, and all other address lines, logiclow (see Table 2).

The second GAL, IC4, is pro-grammed to function as a dual BCD -to -7 segment decoder (see Ref. 1),turning the output codes supplied byoctal bistable IC3 (74HCT273) directlyinto drive signals for the LED seg-

ments. Current limiting is provided bya resistor network. Apart from reduc-ing the component count, the GAL alsoextends the possibilities of most con-ventional BCD -to -7 segment decodersby being able to display hexadecimalnumbers also. The 7 -segment LED dis-plays are common -cathode types. Thecurrent flow is, therefore, from thepositive supply line, via the GAL out-puts, current limiting resistors (220 SI)and a transistor c -e junction, toground.

Circuit IC2 divides the system clockdown to a value suitable for multiplex-



POST Codes - AMI BIOS 2.2X

00 : Flag test

03 : Register test

06 : System hardware initialization

09 : BIOS ROM checksum

OC : Page register test

OF : 8254 timer test

12 : Memory refresh initialization

15 : 8237 DMA controller test

18 : 8237 DMA initialization

1B : 8259 interrupt controller initialization

1 E : 8259 interrupt controller test

21 : Memory refresh test

24 : Base 64K address test

27 : Base 64K memory test

2A : 8742 keyboard self test

2D : MC146818 CMOS test

30 : Start first protected mode test33 : Memory sizing test36 : First protected mode test

39 : First protected mode test failed

3C : CPU speed calculation

3F : Read 8742 hardware switches

42 : Initialize interrupt vector area

45 : Verify CMOS configuration

48 : Test and initialize video system

4B : Unexpected interrupt test

4E : Start Second protected mode test

51 : Verify LDT instruction

54 : Verify TR instruction57 : Verify LSL instruction

5A : Verify LAR instruction

5D : Verify VERR instruction

60 : Adress line 20 Test

63 : Unexpected exception test

66 : Start third protected mode test

69 : Address line test

6C : System memory test

6F : Shadow memory test

72 : Extended memory test

75 : Verify memory configuration78 : Display configuration error messages

7B : Copy system BIOS to shadow memory

7E : 8254 clock test

81 : MC146818 real time clock test

84 : Keyboard test

87 : Determine keyboard type

8A : Stuck key test

8D : Initialize hardware interrupt vector90 : Math coprocessor test93 : Determine COM ports available

96 : Determine LPT ports available

99 : Initialize BIOS data area

9C : Fixed/Floppy controller test

9F : Floppy disk test

A2 : Fixed disk test

A5 : External ROM scan

A8 : System key lock test

AE : Fl error message testAF : System boot initializationB1 : Interrupt 19 boot loader

Address line A9 A8 A7 A6 A5 A4 A3 A2 Al AO

Decimal 512 256 128 64 32 16 8 4 2 1

Hexadecimal 200 100 80 40 20 10 8 4 2 1

Table 2. Card address selection. Example: using address lines A8 and A9 selects address300H (100H + 200H = 300H).

74k4 c\1'14-\-

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00

0 0 0 0 )1 00000000 00

0000 gum0 000 a00 00/

8 memo a

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00000818 000 000

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Table 1. POST codes for version 2.2 of the Fig. 2. Track layout (direct reading) and component mounting plan of the P.O.S.T. diagnosticBIOS supplied by American Megatrends Inc. insertion card. The upper part (display) may be cut off and fitted separately at an angle of 45°.



ing the displays. Both GALs used inthis circuit are supplied ready -pro-grammed through our ReadersServices.

The four LEDs in the circuit indi-cate the presence of the following sup-ply voltages (LEDs left to right on theboard): +5 V, +12 V, -12 V, + 12V. Itshould be noted that these LEDsmerely provide a yes/no indicationabout the presence of the relevant sup-ply voltage - they do not provide infor-mation on the exact levels. If you seekassurance, use your multimeter to es-tablish the exact voltage levels.

As already mentioned, the DIPswitch allows you to set the port ad-dress required for your specific brandof computer. Consult Table 3 for thesetting you need.

Build a P.O.S.T.cardThe card can be built successfully byanyone who works accurately, anduses the printed circuit board suppliedthrough our Readers Services. The art-work of this printed circuit board isgiven in Fig. 2. The board may be cutinto two to separate the control sectionfrom the display section. Depending onyour specific application, you may alsoleave it intact, however.

As usual, start the construction byfitting the low -profile passive parts, re-sistors and capacitors. Proceed with

continued on p. 64

COMPONENTS LIST

Resistors:Ri;R2 = 11(525R3;R4 = 47052R5-R5;Rls;Ri5= 10k0Ri0-Ri2 = 220Q

Capacitors:C1 -C4= 100nF

Semiconductors:D1 D4 = LED, red, 3mm dia.D5;D6 = BAT85T1;1-2= BC547BIC1 = GAL20V8 (order code 946639-1,see page 78)IC2 = 74HCT4040IC3 = 74HCT273IC4 = GAL22V10 (order code 946639-2,see page 78)LD1;LD2 = HD11070 (Siemens)

Miscellaneous:S1 = 5 -way DIP switch.Printed circuit board plus 2 pro-grammed GALs, set order code950008-C (see page 78).

PC DIAGNOSTIC HARDWAREMarket research for 8- and 16 -bit PC diagnostic cards shows that there arerelatively few products available. On being approached for photographs anddescriptions of their products, only one manufacturer of P O.S.T diagnosticcards, Industrial Computer Sources, responded positively. Three of their productsare briefly described

Diagnostic P.O.S T. Board (model R A.C.E.R. II)This card enables the cause of faults on any PC motherboard, from 8088 to80486, to be traced andevaluated. The results ofthe diagnostic operationare shown on the PCscreen, a set of LEDdisplays, or on a printer.

Advanced 16 -bitDiagnostic Card (modelPHD16)This is an even morepowerful card than theR.A.0 E.R The PI -1016runs a large number oftests in a wide range ofhardware sub -sections,including DMA (directmemory access) and IRQ(interrupt request). Thanks to the intelligent electronics on this card, it uses onlya small number of functions of the system under test. Consequently, the board isable to locate faults on motherboards which look absolutely 'dead'.

Micro-ToolkitThis kit, manufactured by 2000 Micro Diagnostics2, and supplied via IndustrialComputer Source,contains a diagnosticprogram called 'Micro -Scope', a P.O.S.T.diagnostic card, and aP.O.S.T. probe. Armedwith these powerful toolsyou should be able totrace and eliminate anymalfunction on a PCmotherboard Extremelyeffective, the kit evenallows low-levelformatting of hard disks(including IDE types). Italso has its ownexamination system, andenables all types ofmemory to be tested,including cache, video,RAM, etc.

The following P.O.S T diagnostic cards are also available, unfortunately noproduct descriptions were received from the relevant manufacturersthe V -ATE Plus from Vista Microsystems, Inc.the POST Code Display from JOE Microdevices

Industrial Computer Source, European Headquarters, Z A de Courtaboeuf, 16 Avenue duQuebec, B P. 712, F-91961 Les Ulis Cedex, France. Tel (+33) 1 69.07 28 22, Fax (+33) 1 64 46 40 42UK readers please contact Industrial Computer Source (UK) Ltd , Birdham Road, Chichester, W.Sussex P020 7EQ, England. Tel. (01243) 533900, fax (01243) 5329492 Micro 2000, Inc. 1100 East Broadway, Suite 301, Glendale, CA 91205, U S.A. Tel (+1) 818/547-0125 or (+1) 800 864-8008, fax (+1) 818/547-0397UK readers please contact Micro 2000 Europe, P.O Box 2000, Letchworth, Herts SG6 1UT, Tel.(0462) 483483, fax (0462) 481484.



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STROBE LIGHT. Bright strobe lightwith an adjustable frequency of 1-60hz.(a lot faster than conventional strobes!)£16 kit, L20 built.

FM TRANSMITTER 3 RF stages,audio preamp. 12-I8vDC. Mediumpowered bug L20 kit, £28 built.3 CHANNEL LIGHT CHASER. 3x800w output, speed and direction con-trols, can be used with 12 led's (sup-plied) or TRIACS for mains lights (alsosupplied). 9-15v DC. £17 kit, £23 built.25W FM TRANSMITTER. 4 stage, apreamp will be required. (Our preampbelow is suitable) £79 built.(no kits).SOUND EFFECTS GENERATOR.Produces any thing from bird chips tosirens! add sounds to all sorts of things£9 kit £13 built.FM/AM SCANNER. Well notquite,you have to turn the knob yourselfbut you will hear things on this radio(even TV) that you would not hear onan ordinary radio! A receiver that cov-ers 50-160MHZ both AM and FM. Builtin 5w amplifier. £15 kit, £20 built.CAR ALARM SYSTEM. Works onvibration and/or voltage drop from dooretc being opened. Entry and exit delaysplus adjustable alarm duration.Low costprotection! £12 kit, £16 built.15W FM TRANSMITTER. 4 stage,high power bug. You will need a preamp

for this (see our preamp below which isok) £69 built. (no kits).1W FM TRANSMITTER. 2 stage in-cluding preamp and mic. Good generalpurpose bug. 8-30VDC.£12 kit,i/ 6 built.

BULK PACKSPREAMP MIXER. 3 channel input,independent level and tone controls.Ideal for use with the hi power FMtransmitters. £15 kit, £19 built.TREMBLER ALARM. Designed forbikes etc, adjustable sensitivity, presetalarm time, auto reset. Could be adaptedfor all sorts of "borrowable" things f 12kit,E16 built.ULTRASONIC RADAR. A projectthat can be used as a movement detector

in an enclosed space. Range about 10metres,12vDC. Good basis forcar,shed,caravan alarm etc.L14 kit, £19built.PIIONE CALL RELAY. Very usefulkit that incorporates a relay that oper-ates when the phone rings. Can be usedto operate more bells, signalling lightsetc. Good for noisy enviroments or ifyou have your headphones on! El 0 kit,£14 built.PORTABLE ALARM SYSTEM.Small 9v alann system based on a mer-cury switch. The alarm contitues tosound until disabled by the. owner.Buzzer included. £11 kit £15 built.800W MUSIC TO LIGHT EFFECT.Add rhythm to your music with thissimplesound to light kit. L8 kit, £12built.MOSQUITO REPELLER. Modemway to keep the midges away! Runs for

about a month on oneI.5v battery. Frequency is

set to drive away mosquitos etc. E7 kit,£11 built.3 CHANNEL SOUND TO LIGHT.Can be used anywhere as no connectionis made to hi fi. Separate sensitivitycontrols for each channel,1,200Wpowerhandling. Microphone'included. £14 kit, £19 built.MINI METAL DETECTOR. Detectspipes,wires etc up to 20cm deep. Use-ful before you drill those holes! L8 kit,£12 built.0-5 MINUTE TIMER. Simple timeswitch adjustable from 0-5 mins,willswitch 2A mains load. 12v op. Ideal forlaboratory, photographic projects etc.L7 kit, El 1 built.7 WATT III Fl AMPLIFIER Useful,powerful amplifier 20hz-15hz, 12-18vdc. Good for intercoms, audio sys-tems, car etc. E7 kit LI I built.INCAR SOUND TO LIGHT. Putsome atmosphere in your car with thiskit. Each channel has 6 led's that create

a beautiful lighting effect! £10 kit, £14built.VOX SWITCH. This is a sound acti-vated switch, ideal for use on transmit-ters, CB's, tape recorders etc. Adjust-able sensitivity, built in delay. Mic in-put. £7 kit, £11 built.

50 I/C's for £1.50Nice mix of chips at a bargain price!

CERAMIC CAPACITOR PACKGood mixed pack of 100 capacitors

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ELECTROLYTIC PACK 1100 small mixed electrolytic

capacitors just ELOOELECTROLYTIC PACK 250 larger electrolytic mixed

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FUSE PACK NO 230 mixed 1.25" fuses again ideal for

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WIRE PACK25 Metres of insulated wire for just

£1.00, good for projects etc.

SLEEVING PACK100 assorted pieces of sleeving for

connectors etc. Yours for just £1.00

RESISTOR PACK NO 1250 low wattage resistors, ideal for

most projects etc. Just L1.00

DIODE PACK100 assorted diodes for just £1.00

LED PACK20 light emitting diodes for £1.00

RESISTOR PACK NO 2Hi wattage pack, good selection of

mixed wattages and values 50 in all,bargain price just £1.00

TRANSISTOR PACK50 mixed transistors, another bargain

at £1.00

PRESET PACKNice selection of 25 mixed preset

pots for just another LI!

BUZZER PACK10 things that make a noise for just

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RELAY PACK NO 16 mixed relays for LI, thats just 17p

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POT PACK10 pots for £1, (5 different types) a

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CONNECTOR PACK10 different connectors, again for £1

FUSE PACK NO 140 mixed 20mm fuses, ideal for

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DISPLAYS10 seven segment displays for

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KITS 'N MODULESLIQUID LEVEL DETECTOR.

Useful item, can be used to detectfluid levels in watertanks, baths, pondsfishtanks etc. Could also be used as rainalarm with an easily constructed sm-sor. £5 kit, L9 built.FM TRANSMITTER. Mini FM trans-mitter 2 transistor, comes with FETminaturemic and is tuneable from 63 to130MHZ. L7 kit, Et I built.FUNCTION GENERATOR. Gener-ates sinusoidal, saw tooth and squarewaveforms from 20hz up to 20khz. Separate level controls for each waveform.24vac. £15 kit, L20 built.5 WATT SIREN. Powerful siren kitwith an impressive 5 watts output. Idealfor alarms etc. Lb kit L10 built.TELEPHONE AMPLIFIER. Verysensitive amplifier which using a 'phonepickup coil (supplied) will let you fol.,

low a telephone conversation withoutholding the handset to your ear! LI 1 kit£15 built.

SWITCH PACK10 switches for just £1 .00

12v FLOURESCENT. A useful kit thatwill enable you to light large flourescenttubes from your car battery etc. 9v mainstransfonner required. L8 kit, £12 built.

KNOB PACK10 knobs for just L1.00

REMEMBER! YOUR FREE COPYOF OUR CUT PRICE COMPO-

NENTS CATALOGUE SENTWITH EVERY ORDER!!!

How to place your orderBy phone 0273 771156By FAX 0273 206875By Post...PO box 517 Hove Sussex BN3 5QZPayment by ACCESS,VISA, CHEQUE OR POSTAL ORDER.Cheques and postal orders should be payable to Express Components.ALL PRICES ARE SUBJECT TO 99p POST AND VAT. Some of our products

may be unlicensable for use in the UK (particularly the FM transmitters.)



WI 1994/5

The Winter 94/95 edition has 280 pages packedwith over 4000 products and now with news andfeatures including two full construction projects

New additions to Cirkits' unique range of kits, including:Infra -red Remote Control SystemCombustible Gas DetectorMains Carrier Audio LinkMains Carrier Remote ControlElectrical Appliance Watt MeterBreath TesterTV AudioNideo Tuner

R Two feature projects, fully detailed articles for Hi-Fiquality Infra -red Cordless Headphones and `Chiptester'a logic IC tester with full PC software, with fullconstruction kits available for both

IV Many more additions throughout the catalogueincluding mobile phone batteries and chargers, low costthermometers, timers, ICs, LEDs, test equipment,books, opto couplers and much more

280 pages, 26 sections, over 4000 products from someof the worlds finest manufactures and suppliers

1111 Available from 20th October at most large newsagentsor direct from Cirkit

P Send for your copy today!

CirkitCirkit Distribution Ltd

Park Lane Broxbourne Hertfordshire EN10 7NQTelephone (0992) 448899 Fax (0992) 471314

so

The BASIC Stamp by PARALLAX is a true microcomputer that runs

BASIC programmes written on your PC. Its size, ease of use and extensive

I/O features make it an ideal tool for both educational and industrial

applications, as well as the serious hobbyist.

Writing programmes for the Stamp is easy. A 3 -pin cable connects

the Stamp to your PC's parallel port. One piece of software is all that is

used to enter, debug and download your programme. BASIC functions

include serial communications, pulse measurement, button de -bounce,

tone generation and PWM; all achieved with a minimum of extra

components - if any at all.

The BASIC Stamp Development Kit at f99 includes:

1 BASIC Stamp, a very readable instruction manual,

PC connection cable, software and extensive application notes

to get you up and running in minutes!

)o- Further Stamps cost only f33 each.(All prices excl VAT and £3 postage per order.)

For an information pack on the BASIC Stamp and other creative

products please call our 24 -hour answerphone on 0977 683665.

MILFORD INSTRUMENTS24 hr Answerphone - 0977 683665Milford House, 120 High Street, South Milford, LEEDS LS25 5AQ

THE BASIC STAMP ALBUMa collection of the mostinnovative Stamp applications

3 IASI( instructions are all rt takes to read the potand output o proportional tone. Our applicationsheets cover this and many other uses for the Stomp.

Send YOUR application for inclusion In the

BASIC Stamp Albem, every application

published will be uckuowledged,

PLUS the best application each month

will receive 2 FREE BASIC Stamps.


64 S

PC DIAGNOSTIC SOFTWAREIt will be clear that the programs mentioned here are only useful if the essential hardware of the PC is functional. This goesfor commercially available programs such as Checkit, Checkit Analyst and QuickTech Pro, as well as those in the sharewaredomain. So, hardware debugging goes logically before running any of the programs mentioned in this inset.

CheckIt-Pro diagnostic software is typical of its class. The program ensuresdirect access to the most essential (i.e., critical) functions of the system, usingrigorous tests on the CPU, all types of memory, internal as well as externalcache devices, video, RAM, etc. It also scrutinizes each and every peripheraldevice (plug-in cards) connected to the motherboard, including parallel andserial ports, the keyboard, video cards, hard disk, and others.

Checklt Analyst was also examined as part of the research carried out forthis article. The program can be run on DOS, Windows or OS/2 platforms.

Great performance if you are after elusive faults in, say, the realmsof IRQ, memory or input output addresses.

3 31

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Troubleshooter also runs extremely intricate tests on all systemcomponents, from CPU to peripherals and, of course, the memory(which for some reason seems to be the most troublesome area). Iteven does a quick test on a CD-ROM player (hard to imagine,though, with, say, a PC/XT clone) and a sound card, if installed.

Surprisingly, there is a program which most of you will have butappears to be little known. MSD, MicroSoft Diagnostic, is includedin your Windows 3.1 (and later) package, and can be found in theWindows subdirectory. It should be noted, however, that the firstaim of MSD is to establish exact system configurations, rather thanassisting in locating hardware faults.

au,tim repoits a PC/AT ComputerMS DOS Ile ---- System Info Plus Ver 3 21 Copyright (C) 1993 cALMER Utilities (tm)Mous( Dev Line 16/ Column 1 <Print Screen> for printout, <Esc> exits this programMouse ButMouse DiaMouse DriMouse TypMouse IntMouse/EGAEquipmentfloppy dihard diskDOS repor1 PordlleTime-out3 SerialTime outMETBaud rateData bits

Drive C Disk ClassDrive C is

Disk TypeDisk Serial NumberOriginal LabelDisk formatted underFirst Systems FileSecond Systems FileThird Systems FileNumber of Disk headsReserved SectorsSectors per TrackNumber of TracksSectors per ClosterTotal Clustersmax Files in rootBytes FreeRoot Dir starts SecHidden Sectors

Hard DiskMOT removable and is MOT a Network device

: Fixed disk: 1D4F-70C9

: MSD065.0 Disk is bootable1U.SYS 30 Sep 93 06:20:00

MSDOS.SYS 30 Sep 93 06:20:00C20DOS,COMMAND.COM 30 Sep 93 06:20:80

13 Number of Sectors8 Bytes per Sector

51 Sectors per Pat9,375 Bytes per Cluster

Free Clusters59 766 Number of Fats

512 Capacity (bytes)180 756 480 First Data Sector

469 sectors occupied51

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Among the best known diagnostic programs in the shareware domain are S.I. Plus v3.21 (SIPLU321.ZIP) andConfiguration v7.27e (CONF727E.ZIP), which can found on numerous bulletin boards. The reports created by theseprograms are very useful if you need to locate and eliminate possible problem sources.

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inserting the ICs into their sockets,taking care to observe the proper ori-entation. Also be sure to fit the rightGAL into the right socket - these de-vices do not have the same function!The board is not fitted with the usualsupport bracket at the rear side be-cause it is not intended to remain per-manently inside the PC.

Testing the test cardThe completed card is first insertedinto one of the free slots of a functionalPC. Next, run the Pascal programlisted in Fig. 4. It is recommended touse the card at base address 300H,which, according to the IBM PC speci-fication, is reserved for experimenting.This address is selected by closingonly Sid on the DIP switch block. Thecard is functional if the compiled pro-gram produces an incrementing num-ber on the LED display and the PCscreen every time you press CR. Note,however, that the LED display readoutis hexadecimal, while the numbers onthe PC screen are in decimal.

If the P.O.S.T. card does not passthis test, you have probably made aconstruction error. Start by verifyingthe presence of a clock signal at pin 11of latch IC3. If this signal is present,check the latch outputs, which shouldsupply copies of the latch input sig-nals. If this test also checks out, theonly likely cause of the malfunctionthat remains is either GAL IC4 or oneof the 7 -segment LED displays.

In case of trouble...The P.O.S.T. code display card de-scribed here does not pretend to be areplacement of much more powerfulPC diagnostic cards available commer-cially. Rather, its function is that of anauxiliary tool. None the less, the pre-sent card is extremely valuable if youwish to bring back life to, say, an old286 motherboard which does not evenproduce error beeps on being powered.As already mentioned, the aim is to getpast the initial test routines (P.O.S.T.mortem!), and make sure that the rele-vant motherboard can load at least theDOS again. From there on, you are in aposition to run hardware/software di-agnostic tools such as Norton, CheckItand PCTools.

The P.O.S.T. code displayed by thecard supplies a possible cause of theproblems experienced with either acomponent on the motherboard, amemory module, or one of the inser-tion cards. If the fault appears to be inan extension card, it is relatively sim-ple to resolve by a visit to your localcomputer shop and replace the culprit.On the other hand, if the problem is atlevel of, say, the DMA or interrupt con -

Address PC type/brand DIP switch S1

60H XT (default value) none closed

80H AT/386/486/Pentium Si, closed84H Compaq Sid closed

90M PS/2 -30 with ISA bus Sic closed

280H Clones (including someCompaq PCs) Sib closed

300H EISA bus systems Sia closed

Table 3. Overview of P.O.S.T. card addresses used in different computer types and brands.

Fig. 3. Completed prototype of the P.O.S.T. diagnostic card. Note that this version differsslightly from the final design.

troller, or any other complex ASIC orGAL on the motherboard, replacementor repair is probably not worth the ef-fort, and the motherboard is bestchucked into the bin after removingthe RAM and CPU parts. Incidentally,replacement motherboards with emptyCPU sockets may be obtained at verylow prices these days. Regrettably,though, it seems almost impossible toobtain spares of the ICs that form theso-called chip set (Neat, etc.) on themotherboard, while desoldering andre -fitting these jumbos' is really out ofthe question without very special tools.

(950008)

Reference:1. Hexadecimal display decoder,Elektor Electronics December 1993.

program testpostcard;uses dos, crt;

const post = $300;var

i : word;

dummy : char;

beginfor i:=0 to $ff do

beginport[post]:=i;

writeln (i);repeat until keypressed;dummy:=readkey;

end;

end.

Fig. 4. Listing of the test program for theP.O.S.T. diagnostic card (Pascal). Changethe value of constant 'Post' as required foryour specific brand and type of PC.



Appendix: PC BIOS P.O.S.T codes

POST Codes - AMI BIOS POST

01 NMI disabled & 286 reg test about to start

02 286 register test over

03 ROM checksum ok

04 , 8259 initialization ok

05 CMOS pending interrupt disabled

06 . Video disabled & system timer counting ok

07 CH -Q of 8253 test ok

08 CH -2 of delta count test ok

09 , CH -1 of delta count test ok

OA CH -0 of delta count test ok

08 Panty status cleared

OC Refresh & system timer ok

OD Refresh link toggling ok

GE Refresh period ON/OFF 50% ok

10 Confirmed refresh ON & about to start 64K memory

error

11 Adress line test OK

12 64K base memory test ok

13 Interrupt vector initialized

14 , 8042 keyboard controller test ok

15 CMOS read/write test ok

16 CMOS checksum/batery check ok

17 , Monochrome mode set ok

18 Color mode set ok

19 About to look for optional video ROM

1A ; Optional video ROM control ok

1B Display memory R/W test ok

1C Display memory R/W test for alternative display ok

10 Video retrace check ok

1E Global equipment byte set for video ok

1F , Mode set call for mono/color ok

20 Video test ok

21 Video display ok

22 Power on message display ok

NOTE . The "oh' appearing after many of these POST

codes means that particular code line has executed

successfully It does not necessarily mean that the

component to which the code refers has passed or

failed.

30 Virtual mode memory test about to begin

31 , Virtual mode memory test started

32 Processor in virtue! mode

33 Memory address line test in progress

34 Memory address line test in progress

35 Memory below 1MB calculated

36 Memory size computation ok

37 Memory test in progress

38 Memory initialization over below 1MB

39 Memory initialization over above 1MB

3A Display memory size

3B: About to start below 1MB

3C Memory test below 1MB ok

3D Memory test above 1MB ok

3E About to go to real mode (shutdown)

3F Shutdown successful and entered into real mode

40 About to disable gate A-20 address line

41 , Gate A-20 line disable successfully

42 About to start DMA controler test

4E Address line test ok

4F , Processor in real mode after shutdown

50 DMA page register test ok

51 DMA unit -1 base register test about to start

all trademarks acknowledged. E. & O.E.

52 . DMA unit -1 channel ok, about to begin CH -2

53 . DMA CH -2 base register test ok

54 About to test f/f latch for unit -1

55 f/f latch test both units oh

56 DMA units 1 & 2 programmed ok

57 8259 initialization over

58 8259 mask register check ok

59 . Master 8259 mask register ok, about to start slave

5A : About to check timer and keyboard interrupt level

5B . Timer interrupt ok

5C About to test keyboard interrupt

5D , ERRORI timer/keyboard interrupt not in proper level

5E 8259 interrupt controller error

5F 8259 interrupt controller test ok

70 Start of keyboard test

71 Keyboard BAT test ok

72 Keyboard test ok

73 Keyboard global data initialization ok

74 : Floppy setup about to start

75 Floppy setup ok

76' Hard disk setup about to start

77 Hard disk setup ok

79 About to initialize timer data area

7A Verify CMOS battery power

7B , CMOS battery verification done

7D About to analyze diagnostics test result for memory

7E CMOS memory size update ok

7F About to check optional ROM C000 0

80 Keyboard sensed to enable SETUP

81 Optional ROM control ok

82 Printer global data initialization ok

83 RS232 global data initialization ok

84 80287 check/test ok

85 . About to display soft error message

86 About to give control to system ROM E000 0

87 : System ROM E000,0 check over

00 Control given to interrupt 19, boot loader

POST Codes - AWARD BIOS 3.3

01 Keyboard controller (8042)

02 0

03,"04

05

06 On -board LSI 07 CPU

08 . CMOS 8254, 8237, 8257 & EPROM

09

OA 0

OB

OC

OD

OE <i

OF Extended CMOS

10 Refresh

11'« 012 0

13 «

14 :

15 First 64K RAM

16 Interrup vector tables

17 . Video initialization

18 Video memory

19 : interrupt line mask

1A

1B Battery good

1C , CMOS checksum

1D CMOS chip

1E Memory size

1F Memory verifier

20 CPU support chips

21

22

23

24 . Protected memory size

25 Protected memory test

26 Protected mode

27 Shadow RAM, cache controller

28 «

29 : Reserved

2A Initialize keyboard

2B Floppy drive Initialization

2C Senal port initialization

2D Parallel port initialization

2E Hard disk initialization

2F Math coprocessor

30 Reserved

31 Optional ROMs

FF Boot

POST Codes - CHIPS and TECHNOLOGIES

00 Error in POS registers

01 Flag register failed

02 ' CPU register failed

03 System ROM failed checksum

04 DMA controler failed

05 System timer failed

06 Base 64K failed address test

07 Base 64K failed ram test

08 Interrupt controller failed

09 Hot interrupt occurred

OA Timer failed to generate interrupt

OB CPU still in protected mode

OC DMA page registers failed

OD refresh not occurring

OE Keyboard controller not responding

OF: Could not enter protected mode

10 GDT or IDT faded

11 LOT register failed

12 Task register failed

13 , LSL instruction failed

14 LAR instruction failed

15 VERRNERW failed

16 Keyboard controller A20 failed

17 Exception failed / unexpected

18 Shutdown during memory test

19 Last used error code

lA Copyright checksum error

1B . Shutdown during memory sizing

1C CHIPSet initialization

50 Initialize hardware

51 , Initialize timer

52 . DMA mit

53 8259 mit



54 : Imtiahze CHIPSet

55 : Set up BMS configuration

56 : Entering protected mode for first time

57 : Size memory chips

58 Configure memory chip interleave

59 Exiting protected mode for first time

5A Determine system board memory size

5B Relocate shadow RAM

5C Configure EMS

5D Set up wait state configuration

5E Re -test base 64K RAM after RAM sizing

5F Test shadow RAM

60 CMOS test

61 Video test

63 Protected mode interrupt test

64 Test line A20

65 Test Memory addredd lines

66 Memory test

67 Extended memory test

68 Timer interrupt test

69 Real-time clock (RTC) test

6A Keyboard test

68 Coprocessor test

6C Seriel port test

60 Parallel port test

6E Dual card test

6F : Floppy drive controller test

70 : Fixed disk test

71 : Keylock test

72 Pointing device test

90 RAM setup

91 Calculate CPU speed

92 Check configuration

93 BIOS initialization

94 POD bootstrap

95 Reset ICs

96 PUS select

97 VGA power on diagnostic and setup

98 Adapter POS

AO Exception 0 during POD

Al Exception 1 during POD

A2 Exception 2 during POD

CO System board memory failure

Cl I/O channel check activated

C2 Watchdog time out

C3 Bus time out

POST Codes - COMPAQ (i/o at 280h, NOT at 80h!)

00 Initialize flags, MSW, IDTLIN

01 Read manufacturing juniper

02 8042 received read command

03 No reponse from 8042

04 Look for manufacturing ROM at E0000

05 Look for manufacturing ROM at 08000

06 No manufacturing ROMs

07 Read CMOS reset code

08 intialize 8259, 80287

09 Jump indirect indexed by reset code

OA Vector via 40 67 reset function

OB Vector via 40:67 with E01 function

00 Boot reset function

00 , Test #2 8254 counter 0

OE Test #2 8254 counter 2

OF Warm boot

Overall Power Up Sequence Codes

10 PPI disabled, program times 0 & 1

11 Initialize (blast) VDU controllers

12 Clear screen, turn on video

13 Test timer 0

14 Disable RTC interrupts

15 Check battery power

16 Battery has lost power

17 Clear CMOS DIAGS

18 Test base memory first 128K)

19 Clear and initialize base memory

1A Initialize and test VDU adapters

1B Test the system ROM

1C Test CMOS

1D Test DMA controller and page registers

1E Text keyboard controller

1F Test 286 protected mode

20 , Test real and extended memory

21 initialize time -of -day

22 Initialize 287 coprocessor

23 Test the keyboard and interface

24 Reset A20 and set default CPU speed

25 test diskette subsystem

26 , Test fixed disk subsystem

27 Initialize parallel printer

28 Perform search for optional ROMs

29 Test for valid system configuration

2A Clear screen

2B : Check for invalid time and date

2C Optional ROM search

2D Test timer 2

2F Write to DIAG byte

Base RAM Initialization Codes

30 Clear first 128K bytes of RAM

31 Load interrupt vectors 70-77

32 Load interrupt vector 00-1F

33 Initialize MEMSIZE and RESETWD

34 Verify CMOS checksum

35 , CMOS checksum is not valid

36 Check battery power

37 Check for game adapters

38 Check for serial ports

39 Check for parallel printer ports

3A Initialize prt and comm timeouts

39 Flush keyboard buffer

Base RAM Test Codes

40 Save RESEW value

41 Check RAM refresh

42 Start write cycle of 128K RAM test

43 Reset parity checks

44 Start verify cycle 128K RAM test

45 Check for parity errors

46 No RAM errors

47 RAM error detected

VDU Initialization and Test Codes

50 Check for dual frequency in CMOS

51 Check CMOS VDU configuration

52 Start VDU ROM search

53 Vector to VDU option ROMs

54 Initialize primary display adaptor

55 Initialize secondary display adaptor

56 No display adaptaters installed

57 Initialize primary VDU mode

58 Start of VDU test (for each adaptor)

59 Check existence of adaptor

5A Blank display, check VDU registers

5B Start screen memory test

5C End of test for adaptor, clear memory

5D Error detected on an adaptor

5E Test the next adaptor

5F All adapters successfully tested

Memory Test Codes

60 Start memory test

61 Enter protected mode

62 Start memory sizing

63 Get CMOS size

64 Start test of real memory

65 Start test of extended memory

66 Save size of real and extended memory

67 Uptade 128K option installed CMOS bit

68 Prepare to return to real mode

69 Back in real mode - test successful

6A Back in real mode - error during test

GB Display error messages

6C : End of memory test

6D Initialize KB OK string

Determine size to test

6F Start of MEMTEST

70 Display 000CX KB OK

71 : Test each RAM segment

72 High order address test

73 Exit MEMTEST

74 Parity error on bus after memory test, system halted

80286 Protected Mode Codes

75 Start of protected mode test

76 Prepare to enter protected mode

77 Test software exceptions

78 Prepare to return to real mode

79 Back in real mode - no error

7A Back in real mode - error detected

7B: Exit protected test

7C High order address test failure

7D ' Entered cache controller test

7E Programming memory cacheability

7F Copy system ROM to high RAM

8042 And Keyboard Codes

80 Start of 8042 test

81 , Do 8042 self -test

82 Check result received

83 Error result

84 . OK 8042, ;nit mode = 5D

86 Start keyboard test, reset keyboard

87 ' Got acknowledge, read result

88 Got result, check it

89 Test for stuck key

8A Key seems to be stuck

8B Test keyboard interface

8C Got result, check it

8D End of test, no errors

System Board Test Codes

90 : Start of CMOS test

91 CMOS seems to be ok

92 Error on CMOS read/write test

93 , Start of DMA Controller test

94 Page registers seem to be ok

95 DMA controller is ok

96 8237 Initialization is complete

NCA RAM Test Codes

9A Start of NCA RAM test

Diskette Test Codes

AO Start of diskette tests

Al FDC reset active (3F2h bit 2)

A2 FDC reset inactive (3F2h bit 2)

ELEKTOR ELECTRONICS JANUARY 1995 continued on p 70


Take the

Quickroute £99.00

to successful PCB &Schematic Design

Design PCB's and Schematics quickly

Ouickroute 3.0 -ICAORABIG2.SCH)Lile Edit yiew Tools Options Library Symbol

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Telephone or FAX POWERware on 061 449 7101Quickroute 3.0 for Windovg 3.1DESIGNER £99.00 DESIGNER+ £1 49.00PRO £199.00 PRO+ £299.00All prices exclude post & packing, and V.A.T.

POWERware, 14 Ley Lane,Marpie Bridge, Stockport,SK6 5DD, UK.

DEMODISKAvailable



SURV14.11LLANCEP1HWESSNRAL Malin KITS

Whether your requirement for surveillance equipment is amateur, professional or you are just fascinated by this unique area ofelectronics SUMA DESIGNS has a kit to fit the bill. We have been designing electronic surveillance equipment for over 12 yearsand you can be sure that all our kits are very well tried, tested and proven and come complete with full instructions, circuitdiagrams, assembly details and all high quality components including fibreglass PCB. Unless otherwise stated all transmittersare tuneable and can be received on an ordinary VHF FM radio.

Genuine SUMA kits available only direct from Suma Designs. Beware inferior imitations!UTX Ultra -miniature Room TransmitterSmallest room transmitter kit in the word! Incredible 10mm x 20mm including mic3-12V operation. 500m range £16.45

MTX Micro -miniature Room TransmitterBest-selling micro -miniature Room TransmitterJust 17mm x 17mm including mic. 3-12V operation. 1000m range £13.45

STX High-performance Room TransmitterHi performance transmitter with a buffered output stage for greater stability and range.Measures 22mm x 22mm including mic. 6-12V operation, 1500m range £15.45

VT500 High -power Room TransmitterPowerful 250mW output providing excellent range and performance. Size 20mm x40mm. 9-12V operation. 3000m range £16.45

VXT Voice Activated TransmitterTriggers only when sounds are detected. Very low standby current. Variable sensitivityand delay with LED indicator. Size 20mm x 67mm. 9V operation. 1000m range £19.45

HVX400 Mains Powered Room TransmitterConnects directly to 240V AC supply for long-term monitoring. Size 30mm x 35mm.500m range £19.45

SCRX Sfibcarrier Scrambled Room Transmitter

Scrambled output from this transmitter cannot be monitored without the SCDM decoderconnected to the receiver. Size 20mm x 67mm. 9V operation. 1000m range £22.95

SCLX Subcarrler Telephone TransmitterConnects to telephone line anywhere, requires no batteries. Output scrambled sorequires SCDM connected to receiver. Size 32mm x 37mm. 1000m range £23.95

SCDM Subcarrier Decoder Unit for SCRXConnects to receiver earphone socket and provides decoded audio output toheadphones. Size 32mm x 70mm. 9-12V operation £22.95

ATR2 Micro Size Telephone Recording InterfaceConnects between telephone line (anywhere) and cassette recorder. Switches tapeautomatically as phone is used. All conversations recorded. Size 16mm x 32mm.Powered from line £13.45

*** Specials ***DLTJUDIRX Radio Control SwitchRemote control anything around your home or garden, outside lights, alarms, pagingsystem etc. System consists of a small VHF transmitter with digital encoder and receiverunit with decoder and relay output, momentary or alternate, 8 -way dil switches on bothboards set your own unique security code. TX size 45mm x 45mm. RX size 35mm x90mm. Both 9V operation. Range up to 200m.Complete System (2 kits) £50.95Individual Transmitter DLTX £19.95Individual Receiver DLRX £37.95

MBX-1111-Fl Micro BroadcasterNot technically a surveillance device but a great idea! Connects to the headphone outputof your Hi -Fl, tape or CD and transmits Hi-Fi quality to a nearby radio. Listen to yourfavourite music anywhere around the house, garden, in the bath or in the garage andyou don't have to put up with the DJ's choice and boring waffle. Size 27mm x 60mm.9V operation. 250m range £20.95

0

A

110

UTLX Ultra -miniature Telephone TransmitterSmallest telephone transmitter kit available. Incredible size of 10mm x 20mm!Connects to line (anywhere) and switches on and off with phone use.All conversation transmitted. Powered from line. 500m range £15.95

TLX700 Micro -miniature Telephone TransmitterBest-selling telephone transmitter. Being 20mm x 20mm it is easier to assemble thanUTLX. Connects to line (anywhere) and switches on and off with phone use. Allconversations transmitted. Powered from line. 1000m range £13.45

STLX High-performance Telephone TransmitterHigh performance transmitter with buffered output stage providing excellent stabilityand performance. Connects to line (anywhere) and switches on and off with phone use.All conversations transmitted. Powered from line. Size 22mm x 22mm.1500m range £16.45

TKX900 Signalling/Tracking TransmitterTransmits a continous stream of audio pulses with variable tone and rate. Ideal forsignalling or tracking purposes. High power output giving range up to 3000m. Size25mm x 63mm. 9V operation £22.95

CD400 Pocket Bug Detector/LocatorLED and piezo bleeper pulse slowly, rate of pulse and pitch of tome increase as youapproach signal. Gain control allows pinpointing of source. Size 45mm x 54mm. 9Voperation £30.95

C0600 Professional Bug Detector/LocatorMulticolour readout of signal strength with variable rate bleeper and variable sensitivityused to detect and locate hidden transmitters. Switch to AUDIO CONFORM mode todistinguish between localised bug transmission and normal legitimate signals such aspagers, cellular, taxis etc. Size 70mm x 100mm. 9V operation £50.95

QTX180 Crystal Controlled Room transmitterNarrow band FM transmitter for the ultimate in privacy. Operates on 180 MHz andrequires the use of a scanner receiver or our ORX180 kit (see catlogue). Size 20mm x67mm. 9V operation. 1000m range £40.95

QL)(180 Crystal Cointrolled Telephone TransmitterAs per OTX180 but connects to telephone line to monitor both sides of conversations.20mm x 67mm. 9V operation. 1000m range £40.95

(ISX180 Line Powered Crystal Controlled Phone TransmitterAs per OLX180 but draws power requirements from line. No batteries required. Size32mm x 37mm. Range 500m £35.95

(111X180 Crystal Controlled FM ReceiverFor monitoring any of the '0' range transmitters. High sensitivity unit. All RF sectionsupplied as a pre -built and aligned module ready to connect on board so no difficultysetting up. Outpt to headphones. 60mm x 75mm. 9V operation £60.95

A build-up service is available on all our kits if required.UK customers please send cheques, POs or registered cash. Please add£1.50 per order for P&P. Goods despatched ASAP allowing for chequeclearance. Overseas customers send sterling bank draft and add £5.00 perorder for shipment. Credit card orders welcomed on 0827 714476.

OUR LATEST CATALOGUE CONTAINING MANY MORE NEWSURVEILLANCE KITS NOW AVAILABLE. SEND TWO FIRSTCLASS STAMPS OR OVERSEAS SEND TWO IRCS.



A3' FDC motor on

A4 FDC time-out error

A5 FDC failed reset

A6 FDC passed reset

A8 Start to determine drive type

A9 Seek operation initiated

AF Diskette tests complete

BO Start of fixed dnve tests

B1 Combo board not found, exit

B2 Combo controller failed, exit

B3 Testing drive 1

B4 Testing drive 2

B5 Drive error (error condition)

B6 Drive failed (failed to respond)

B7 CMOS RAM invalid or no fixed drives, exit

B8 Fixed drive tets complete

89 Attempt to boot diskette

BA Attempt to boot fixed drive

BB Boot attempt failed (diskette or fixed)

BC Boot record read, lump to boot record

BD Drive error, retry booting

BE Weitek coprocessor test

DO Entry to clear memory routine

D1 ready to go to protected mode

D2 Ready to clear extended memory

03 Ready to reset back to real mode

04 Back in real mode

D5 Clear base memory

DD self -test failed

Option ROM Replacement

EO Ready to replace E000 ROM

El Completed EON ROM replacement

E2 Ready to replace EGA ROM

E3 Completed EGA ROM replacement

POST Codes - IBM AT

01 80286 processor test (real mode) -flags, regs & cond

imps

02 ROM checksum test - test 32K ROM POST, BASIC &

BIOS

03 CMOS shutdown byte test - rolling bit ptrn

shutdown addr

04 8254 timer 1 all bits ON - set timer count, check all

bits ON

05 . 8254 timer 1 all bits OFF - set timer count, check all

bits OFF

06 8237 DMA 0 int chan reg test disable DMA cont=0,

r/w cur, addr all ch

07 8237 DMA 1 int chan reg test disable DMA contil,

r/w cur addr all ch

08 DMA page register test - read/write all page registers

09 Storage refresh test - verify refresh is occurnng

* 8042 interface test 10 issue self test - check 55H is

received

OA Soft reset

OB Reset 8042

OC Test ok

OD Write byte 0 of 8042 memory

* base 64K r/w memory test - r/w date patters AA, 55, FF,

01 and 00 to first

64K of memory and verity storage addressability

OE fill memory with data

OF Get I/P buffer switch setting

10 Roll error code to MFG PORT

11 Initialize display row count

Verify 286 LGDT/SGDT LIDT/SIDT instruction

12 Test protected mode registers

13 Initialize 8259 int. # controller chip

14 Setup int vector to temp. interrupt

15 . Establish BIOS int call subr. vectors

* Verify CMOS checksum/Battery ok (config ok for id?)

16 Set data segment

17 Set defective baterry flag

18 Ensure CMOS dividers set

19 Set return address byte in CMOS

1A Set temporary stack

* Protected made test and determined memory size -

Runs in protected mode to address all storage, check

(MSW) for protected mode Base memory size saved

Memory size determined with planer & i/o parity disabled

Soft reset check for parity error

1B Segment address 01-0000 (second 64K)

1C: Set or reset 512 to 640 installed fl

Protected mode test and memory size

1 E Set exp memory size determined in CMOS

1F . Test address line 19-23

20 . Cause a shutdown

21 Return 1 from shutdown

* Initialize and start CRT Cont (6845) Test video r/w

reset video enable signal select alpha mode (40*24

b&w) w/r patterns, check addressability

Error :1 long, 2 short beeps (port 80 not used)

22 Enable video signal and set mode, display horizontal

bar on screen,CRT lines interface test, sence ON/OFF

transition of video enable and horizontal sync lines

23 check for advanced video card

24 go to next test

* 8259 Interrupt controller test - r/w interrupt mask

register with Is and Os

Enable interrupt, check for hot interrupt (not expected)

Test interrupt mask regiters

25 Check for hot interrupts

26 : Display 101 error

27 Check the converting logic 106 error

28 check hot NMI interrupts (error 107)

29 Test data bus to timer 2 (error 108)

* 8254 timer checkout - verify that system (0) count

correctly

2A Do test (error 102)

26 Too fast

2C Too slow (error 103)

20 Check 8042 for last command ecepted (error 105)

2F Go to next test if warm start

30 Set shutdown return 2

31 Enable protected mode

33 Next block of 64K

34 Restore checkpoint

35 Keyboard test

36 Check your AA* scan code

38 Error - check 8042 working

3A Initialize 8042

38 Check for ROM in 2K blocks

3C Check for IPL diskette dnve

3D Initialize floppy for drive type

3E Initialize hard file

3F . Initialize printer

40 Enable H/W interrupt if 80287

41 System code © segment code E000 0

42 Exit to system code

43 Go to boot loader diskette attachment test

81 Build descriptor table

82 Switch to virtual mode

FO Set data segment

Fl Interrupt test (programming interrupt 32)

F2 Exceptional interrupt

F3 Verify 286 LOT/SOT, LTR/STR

F4 Verify 286 bound instruction

F5 : Verify push and pop all intruction

F6 : Verify access rights function

F7 : Verify ARPL functions

F8 : Verify LAR function

F9 : Verify LSL instruction

FA Low meg chip select test

POST Codes - IBM PS/2 BIOS

00 CPU sett test

01 32 bit CPU register test, setup system timer

02 System ROM checksum

03 : Test system enable/setup port

04 : Test system POS register

05 : Test Adapter setup port

06 : Test RTC/CMOS shutdown byte

07 : Test extended CMOS location

08 : Test OMA & page register 8 channels

09 : Initialize DMA command & mode registers

OA: Test refresh

OB : Test keyboard controller buffers

OC: Keyboard controller self test

OD: Keyboard controller test continuation

OE : Keyboard self test error

1F : Setup system memory configuration

10 : Test first 512K RAM in real mode

11 : Half system if memory test error

12 : Verify LGOT/SGDR LIDT/SIDT

13 : Initialize programmable interrupt controller #1

14 : Initialize programmable interrupt controller #2

15 : Initialize A20 interrup vectors

16 . Initialize 16 interrup vectors

17 Check power RTC/CMOS power good signal

18 Check RTC/CMOS checksum

19 RTC/CMOS lost power

lA Skip memory test in protected mode if warm reset

16 Prepare for shutdown

1C Setup stack pointer point to the end of first 64K

10 Decide low memory size in protected mode

1E : Save memory size detected

1F Setup system memory split address

20 ' Check for extended memory beyond 64mb

21 : test memory address bus lines

22 Clear panty error and channel check

23 initialize interrupt 00

24 Determine CMOS validity

25 Write keyboard controller command byte

40 Check valid CMOS and video

41 Display error code 160

42 Test PIC #1 & PIC #2 registers

43 : Test PIC #1 & PIC #2 registers with another pattern

44 Check for interrupt with interrupt masked

45 Test NMI

46 : NMI test error

47 Test system timer 0

48 Check stuck speaker clock

49 Test timer 0 count

4A Test timer 2 output

4B Check if timer interrupt occurred


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APOLLOH.P. 8565A 0.01.22000 ......... 040005V.P. 853 with 85090 21001 .. ... E40H.P. 3580A LED 0.5MHz -50001 01000

MS62B With Tracking Generator 10Milt 1700Melt ... 01500POLARAD 6411 10MHt- 18G00ANDOAC82812ln AC8211 700M0s ..... 0.00H.P. 182 Agte 8558 1001018 -1500MHz .. 31500H.P. 141T with 85548& 85528. 50010-6 1.250MHz ... L1200H.P. 141T with 8553B & 8552A 110-1z -110MHs L800MARCONI TF2370. 30Hz 110MHz L1000H.P. 8444 & 8443 Tracking Generators. Available from ..... S300H.P. 141T Main Frame. only. Good Tubes ..............

OSCILLOSCOPE PROBES Swftchable 51:110 (POP 031 ............ E/2.......

Used Equipment Guarantee Manuals supplied If possibleThis lee VERY SMALL SAMPLE OF STOCK. SAE or Telephone for ts. Please check availability before ordering CARRIAGE all units £16

VAT to be added to Total of Goods and Carriage

OF READING®STEWART110 WYKEHAM ROAD, READING, BERKS RG6 IPL gn

Telephone: (0734) 268041 Fax (0734) 351696 Callers Welcome 9am-5.30pm Mon-Frl (until 8pm Thurs)

4C test timer 0 for count too fast or slow

4D Verify timer 0 interrupt

4E Check 8042 ready for command

4F Check for soft reset

50 Prepare for shutdown

51 Start protected mode test

52 Test memory in 64K increments

53 : Check if memory test done

54 . Shutdown system and return to real mode

55 Test for manufacture or regular test

56 Disable keyboard

57 Check for keyboard self test

58 Keyboard test passed

59: Test keyboard interface

5A Configure mouse

58 Disable mouse

5C Initialize interrupt vectors

50 Initialize interrupt vectors

5E : Initialize interrupt vectors

61 Reset floppy drive

62 Floppy drive test

63 Turn floppy motor off

64 Serial port setup

65 Enable real time clock interrupt

66 Configure floppy drives

67 Configure hard drive

68 Enable system CPU arbitration

69 , Scan for optional ROMs

6A Verify serial & parallel ports

613 Setup equipment byte

8051 TOOLSMCC 8051 'C' Compilier £95MCC 8051 'C' Compiler is an integer 'C' like compiler for the MCS51 family.Easily customised for any MCS51 family variant. Comprehensive printeddocumentation. High level language debugger available (£75)

DDC 'C' Compilers £82.50DDC 'C' compilers are integer 'C' compiliers with more functionality than theMCC compiler but more difficult to use. The compilers are available for68HC08/11/16, 8085/86/96, 8051 family. Documentation supplied on disk.

87C751 Software Development Kit £82.50SDK751 Software development package for the Philips 87C751 micro con-troller. Package includes EDITOR, MACRO ASSEMBLER and source levelSIMULATOR/DEBUGGER.

87C750/751 Programmer £125The MICRO/EP750 plugs into the IBM/PC parallel port and can be used toprogram 87C750 and 87C751 devices.

PC Hand Held Bus Monitor £675MIIC101 is a troubleshooting tool for the I2C serial bus developed byPhilips and the ACCESS bus developed by Digital Equipment Corp. inpartnership with Philips.

8051 BOOK £45A very good text on the 8051 architecture, programming and application. Thebook is supplied with free (un-supported) IBM/PC based assembler andsimulator.

Other tools available prices exclude VAT and delivery

Micro AMPS Limited66 SMITHBROOK KILNS,

CRANLEIGH,SURREY GU6 8JJ, UK

Tel: +44(0)1483 268999Fax: +44(0)1483 268397

ACCESS

VISA

6C Setup configuration error

6D Set keyboard typematic rate

6E : Reset page register, boot up system

POST Codes - OLIVETTI PS/2 Compatible BIOS

01 Processor test

02 . Shutdown

03 Interrupt controller initialization

04 Refresh test

05 CMOS periodic interrupt test

06 Timer ratio, CMOS vs Refresh

07 Test first 64K RAM

08 Test the KBC 8742

09 NMI test

OA 8254 test

OB Port 94h test

OC Port 103h test

OD Port 102h test

OE Port 96h test

OF Port 107h test

10 Blank the screen

11 KB/AUX device fuse check

12 : CMOS battery test

13 CMOS RAM checksum test

14 Extended CMOS checksum 0-8K

15 . System board and adapter initialization

16 RAM test and initialization

17 Protected mode register test

18 . CMOS RAM shutdown byte test

19 80286 protected mode test

1A Video option ROM scan

1B EPROM checksum test

1C Interrupt contoller #1 test

10 Interrupt contoller #2 test

1E Interrupt vector initialization

1F CMOS RAM test

20 Extended CMOS rim test

21 CMOS clock test

22 . Clock calendar test

23 : Dummy checkpoint

24 Watchdog timer test

25 : Test RAM from 64K to 640K

26 . Configure memory 640K



41'Pl'' MONEY ROUTE TO ULTIMATE HI-FI0 HART AUDIO KITS -YOUR VALUE FOR

HART KITS give you the opportunity to build thevery best engineered hifi equipment there is,designed by the leaders in their field, using thebest components that are available.Every HART KIT is not just a new equipment ac-quisition but a valuable investment in knowledge,giving you guided hands-on experience of modernelectronic techniques.In short HART is your 'friend in the trade' givingyou, as a knowledgeable constructor, access tobetter equipment at lower prices than the man inthe street.You can buy the reprints and construction manualfor any kit to see how easy it is to build your ownequipment the HART way. The FULL cost can becredited against your subsequent kit purchase.Our list will give you fuller details of all our AudioKits, components and special offers.

AUDIO DESIGN 80 WATT POWER AMPLIFIER.

'i Li it 111 l3

This fantastic John Linsley Hood designedamplifier is the flagship of our range, and the idealpowerhouse for your ultimate hifi system. This kitis your way to get £K performance for a few tenthsof the cost!. Featured on the front cover of'Electronics Today International' this completestereo power amplifier offers World Class perfor-mance allied to the famous HART quality and easeof construction. John Linsley Hood's comments onseeing a complete unit were enthusiastic:- "Theexternal view is that of a thoroughly professionalpiece of audio gear, neat elegant and functional.This impression is greatly reinforced by theinternal appearance, which is redolent of quality,both in components and in layout." Optionsinclude a stereo LED power meter and a versatilepassive front end giving switched inputs usingALPS precision, low -noise volume and balancecontrols. A new relay switched front end optionalso gives a tape input and output facility so thatfor use with tuners, tape and CD players, orindeed any other 'flat' inputs the power amplifiermay be used on its own, without the need for anyexternal signal handling stages. 'Slave' and'monobloc' versions without the passive inputstage and power meter are also available. Allversions fit within our standard 420 x 260 x 75mmcase to match our 400 Series Tuner range. ALL sixpower supply rails are fully stabilised. and thecomplete power supply, using a toroidal trans-former, is contained within a heavy gaugealuminium chassis/heatsink fitted with IEC mainsinput and output sockets. All the circuitry is onprofessional grade printed circuit boards withroller tinned finish and green solder resist on thecomponent ident side, the power amplifiersfeature an advanced double sided layout formaximum performance. All wiring in this kit is pre -terminated, ready for instant use!RLH11 Reprints of latest articles £1.80K1100CM HART Construction Manual £5.50

LINSLEY HOOD 1400 SERIESULTRA HIGH -QUALITY PREAMP

Joining our magnificent 80 Watt power amplifiernow is the most advanced preamplifier ever of-fered on the kit. or indeed made-up marketplace.Facilities include separate tape signal selectionto enable you to listen to one programme whilerecording another, up to 7 inputs, cross record-ing facilities, class A headphone amplifier, can-cellable 3 -level tone controls and many other use-ful functions, all selected by high quality relays.For full details see our list.

LINSLEY HOOD 'SHUNT FEEDBACK' R.I.A.A.MOVING COIL & MOVING MAGNET

PICKUP PREAMPLIFIERS

Modern, ultimate sound systems are evolvingtowards built-in preamplifiers within or near theturntable unit. This keeps noise pickup and trebleloss to a minimum. We now offer two units, bothhaving the sonically preferred shunt feedbackconfiguration to give an accurate and musicalsound, and both having the ability to use bothmoving magnet and moving coil cartridges.Kit K1500 uses modern integrated circuits toachieve outstanding sound quality at minimal cost.The very low power requirements enable this unit tobe operated from dry batteries and the kit comeswith very detailed instructions making it ideal for thebeginner. K1500 Complete kit with all components,printed circuit board, full instructions and fullyfinished case £67.99Instructions only £2.80Kit K1450 is a fully discrete component implementa-tion of the shunt feedback concept and used with theright cartridge offers the discerning user the ul-timate in sound quality from vinyl disks. Can befitted inside our 1400 Preamp, used externally or asa standalone unit. It has a higher power require-ment and needs to be powered from our 1400 Seriespreamplifier or its own dedicated power supply.K1450 Complete Discrete Component RIAA PhonoPreamp £109.58Factory Assembled and Tested £159.58K1565 Matching Audio Grade Power Supply withpotted toroidal transformer and limited shiftearthing system £79.42Factory Assembled and Tested £118.42U1115 Power Interconnect Cable £7.29

SPECIAL OFFERPRECISION Triple Purpose TEST

CASSETTE TC1D.Are you sure your tape recorder is set up to give itsbest? Our latest triple purpose test cassette checksthe three most important tape parameters withouttest equipment. Ideal when fitting new heads.A professional quality, digitally mastered test tapeat a price anyone can afford.Test Cassette TC1D Our price only £10.99

DISK -COUNT efaaakai CD's.Many New Titles This Month

Top quality, Full Digital (DDD) Compact Disks of thegreat classical favourites. Like everyone else wedidn't like the idea of paying silly prices for CD's_After a long search we have now located a source oftop quality classical recordings at prices that makeyou suspect the quality - until you try them! Send forour list of titles.

HART PCB SOLDERING PRACTICE KITYour chance to learn or try your soldering skills on areal Hart printed circuit board! This kit comes with arange of modern components, a typical Hart qualityPCB, a roll of the correct grade of solder and yourfull learning guide. It enables the enthusiast whois uncertain of his, or indeed her, ability to put to-gether and solder a printed circuit to try their handfirst at minimum cost.The instructions explain the right technique andguide even an absolute beginner through the seem-ingly daunting, but in fact very simple, art of makinga good soldered joint.The Hart Printed Circuit Board Soldering PracticeKit represents excellent value for money at only£4.99.

Send or 'phone for your copy of our FREE List of these and many other Kits & Components. Enquiries from Overseascustomers are equally welcome. but PLEASE send 2 IRCs if you want a list sent surface post, or 5 for Airmail.

Ordering is easy. Just write or telephone your requirements to sample the friendly and efficient HARTservice. Payment by cheque, cash or credit card. A telephoned order with your credit card number will

get your order on its way to you THAT DAY.Please add part cost of carriage and insurance as follows: -INLAND Orders up to £20 - £1.50,Orders over £20 - £3.50. Express Courier, next working day £10.

OVERSEAS - Please see the ordering information with our lists.

QUALITYAUDIO KITS

24 hr. SALES LINE(0691) 652894

TECHNICAL BOOKSHELFThe Following are a Small Selection of the Books we

Offer. Full Details are in our Free List."THE ART OF LINEAR ELECTRONICS", John LinsleyHood.Just Out! Hot Off the Press, the definitive electronicsand audio book by the renowned John Linsley Hood.This 300+ page book will give you an unparalleledinsight into the workings of all types of audio circuits.Learn how to read circuit diagrams and understandamplifiers and how they are designed to give the bestsound. The virtues and vices of passive and activecomponents are examined and there are separatesections covering power supplies and the sources ofnoise and hum. As one would expect from this writerthe history and derivation of audio amplifier circuitryhave an entire chapter, as does test and measure-ment equipment.Copiously illustrated this book is incredible value forthe amount of information it contains on the muchneglected field of linear, as opposed to digital, elec-tronics. Indeed it must be destined to become thestandard reference for all who work, or are interestedin, this field.SPECIAL OFFER. With each book purchased you mayrequest a FREE extended index, written by the Author,exclusively from HART,0-7806-0868-4 £16.95Don't forget most of our kits have reprints of articles byJohn Linsley Hood that you can purchase separately.

"TOWERS' INTERNATIONAL TRANSISTORSELECTOR". This will give you the specification, pinconnections, case outline, manufacturer, equivalentsand substitutes for over 27,000 European, Americanand Japanese transistors. Latest update 4 offers over2,000 new entries plus surface mount cross index.1990 432 Pages. 247 x 173.0-572-01062-1 £19.95

"DIGITAL AUDIO AND COMPACT DISCTECHNOLOGY" 2nd Edition. Baert, Theunissenand Vergult. (SONY Europe).A thoroughly well written book covering the wholefield of recording media starting with the Phonographright through to modern professional PCM digitalrecording systems with particular and extensivecoverage on the compact disc. All aspects of therecording and reproduction processes are explainedwith separate chapters on such things as compactdisc encoding and the use of cross interleaveReed -Soloman error correction code (CIRC). Thisbook is of course essential reading for engineers andstudents involved in the field but its very low pricesmakes it ideal for the enthusiast of recorded musicwho wants to know more about the hidden processesgoing on in his CD player.1992/94 248 Pages. 247 x 190.0-7506-0614-2 £17.95

INTRODUCING DIGITAL AUDIO CD, DAT ANDSAMPLING 2nd Edition. Ian R. Sinclair.For enthusiasts, technicians and students.Covers CD and DAT, Philips DCC and Sony Mini Disc,the digital techniques involved are explained non -mathematically.Digital audio involves methods and circuits that aretotally alien to the technician or keen amateur whohas previously worked with audio circuits. This bookis intended to bridge the gap of understanding forthe technician and enthusiast. The principles andmethods are explained, but the mathematical back-ground and theory are avoided other than to state theend product. This second edition has been updatedto include sections on oversampling methods andbitstream techniques. The opportunity has also beentaken to add a glossary of technical terms.1992 168 Pages. 217 x 138. 64 line drawings.ISBN 1870775 22 8 £7.95

"THE ART OF SOLDERING", R. Brewster.Absolutely essential reading for anyone who everpicks up a soldering iron. Written from knowledgegained in a lifetime in the field, this is the first bookever solely devoted to this essential and neglectedskill for all electronic enthusiasts. Covers everythingfrom the correct choice of soldering iron and solderto the correct procedures to follow with many illustra-tions and practical exercises.0-85935-324-3 £3.95

"HOW TO USE OSCILLOSCOPES & OTHER TESTEQUIPMENT", R.A. Penfold, 112 pages. 178 x 111.Publ. 1989.BP267 £3.50Postage on Single Books is £1.50 except for The Art of LinearElectronics, Digital Audio and Compact Disc Technology andThe Towers International Transistor Selector which are £3.50.Two, or more, books are only £4.50, any size, any quantity.

ALL PRICESINCLUDEUK/EC VAT ire

S17ss'pE,LiniTOR FIVITHONIO JANUARY 1995

IN -LINE A/V TESTER FOR LNCs

MOST low -noise converters (LNCsor LNBs) for satellite TV reception

require either a fixed supply voltage of+15 V or one which is switched be-tween +13 and +15 V. This voltage issupplied by the tuner, via the coaxcable. The LNC current consumptionis typically between 100 mA and400 mA. The low-cost V/A tester de-scribed here allows you to detectshort-circuits in the coax cable, andfaults in the tuner. The little instru-ment has a current range of 0-1 A anda voltage range of 10-20 V.

The tester is inserted into the down -lead coax cable between the LNC andthe tuner with the aid of F -type socketsK1 and K2. K1 is the LNC side, while thetuner is connected to K2 via a shortpiece of coax cable. F -type plugs andsockets are generally available fromsatellite TV installers and retailers.

Capacitor C1 provides d.c. insula-tion, but passes the RF signal on thedownlead coax (950-2050 MHz). RFchokes L1 and L2 block the RF signalfor the rest of the circuit, while C2 andC3 decouple the d.c. side for high -fre-quency signals. To prevent undueamounts of stray capacitance and in-ductance in the circuit (causing signalloss), capacitor C1 and the two chokesmust be connected with the shortestpossible leads. For the very same rea-son, a piece of 75-Q coax, W1, is usedto bridge the distance between K1 andC1. The d.c. path is terminated byshunt resistor R1. The indicated 1 -watttype is capable of handling a maxi-mum continuous current of 2 A.Fortunately, most satellite TV tunerslimit the LNC short-circuit current to amuch lower value. In some low-costtuners, the LNC supply fuse blows,

Design by G. Kleine

and will need to be replaced (after rem-edying the cause of the fault).

With the switch, Si, set to the 'A'(ampere) position, the moving coilmeter, M1, is connected in parallel toR1. A series resistor, R2, then limits thefull-scale deflection of the meter to aneffective current of 1 A.

For voltage measurements, theswitch is set to the 'V' position. Since arange of only 10 V to 20 V is required,the voltage across the measurementnetwork and its series resistor, R3, isreduced by 10 V with the aid of zenerdiode D1. The voltage across R4 thenequals the LNC supply voltage minusthe 10-V zener voltage.

Construction hintsThe LNC V/A tester should be housedin a small metal enclosure, preferablydiecast, for which panel -mount F sock-ets are available. The RF chokes con-sist of about 7 turns of 0.5 -mm dia.(24SWG) enamelled copper wire, close -wound, with an internal diameter ofabout 3 mm. No core or former is used.The construction allows large toler-ances, since L1 and L2 serve as RFblocking devices only.

Components C1, L1 and L2 shouldbe fitted as close as possible to thecentre pin of F socket K2. The connec-tion to the other F socket, K1, is madevia a short piece of 75-a coax cable.The screening at both ends of thisshort transmission line is connected tothe ground contacts of the respective Fsocket. C2 and C3, too, must be con-nected with the shortest possible leadsbetween the 'earthy' side of the chokesand ground.

For the rest of the circuit, 'flyingwire' as well as `stripboard' construc-tions may be used.

If you happen to have a moving coilmeter with a different sensitivity thanindicated in the circuit diagram, resis-tors R2 and R3 need to be altered tomatch the f.s.d. (full-scale deflection)current. In case of a short-circuit, re-sistor R1 carries a current of 1 A, caus-ing a voltage drop of 220 mV. Thisvoltage should be made to correspondto the meter's f.s.d. current. That isachieved by the meter's coil resistanceplus the value of R2.

The value of R4, finally, is computedfrom the maximum voltage which oc-curs across R3 (10 V), and the f.s.d.current of the meter you wish to use. Apossibly simpler way to arrive at thecorrect resistance values is to fit a pre-set and just measure out the requiredresistance. (940115)


74

1 -TO -3 -PHASE CONVERTER

Final part - Construction

Design by B. Yahya

Q ince the voltages existing in many partsL3 of the converter may be lethal, greatcare must be taken in the construction ofthe converter. Not only should the usualsafety guidelines be rigidly adhered to,but there should also be no use made ofcheap, often untested, components. It isalso strongly advised to use an isolatingmains transformer during the construc-

B2

C21

(21 R37 10

IC3

C6

C5

R1

135

R1

3

R14

6

11

4

R15

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-R52

9IC13

01 R40 jci °60

tr,

tion and testing.The printed -circuit board shown in

Fig. 5 is double -sided and through -platedand therefore not easily made without theproper tools and equipment.

Start by fitting all passive components,the transformers and the IC sockets on theboard. Note that C4 is fitted at the trackside. Cover the tracks beneath C26 with in -

0 0K7

0- K6

D19

018

017

016

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sulating tape. Then fit regulators IC17 andIC18. Connect the mains to the board andcheck that potentials of +12 V and+5 V exist at the outputs of IC17 and IC18respectively. Next, verify that the +5 Vline is available at all points indicated inFig. 3. Do not insert the meter prod intothe IC socket pins, since that damagesthe sockets beyond repair.

If all voltages are correct, switch off themains and mount IC1, IC2, IC3, IC4 and IC5.Switch on the mains again and check thatthere is a signal of 1 MHz at pin 1, and PWMsignals at pins 2, 3 and 4, of IC5. If thesesignals are absent, the processor is notworking properly. In that case, check allprevious work thoroughly.

Interconnect K2 and K4, and verify thatthe PWM signals on pins 2, 3, and 4 of IC5 varywhen P5 is turned. These signals shouldalso be present at the six outputs of IC5,

C25

0

e K5

U V

C26

I

R34 10940077-1

Fig. 5. Printed -circuit board for the 1 -to -3 -phase converter - see also pages 75 and 76.


1 -TO -3 -PHASE CONVERTER - PART 2

a 940077 -2 -lib b

Fig. 6. There are two ways of fitting the main heat sink.

provided D7 does not light. This LED maybe made to light by interconnec-ting pins4 and 5 of IC13, IC14 or IC15. It will extin-

0 0 0

940077-1frarik\ell

guish (after about 4 seconds) when thelinks between 1C2 and K4 and pins 4 and5 of the relevant optoisolator have been re -

0

00 01:0

0

0

moved. Switch off the mains.Mount the remaining semiconductors

and integrated circuits. Note that like nor-mal MOSFETs the IGB I module is vulnerableto static electricity.

If motors 100 W are to be used, thereis no need for a heat sink for IC12; at higherpowers, this is a must. There are two waysof cooling, which are illustrated inFig. 6; which of these is chosen dependson the application of the converter.

In Fig. 6a, the IGBT, mounted on aheat sink which also houses the NTC, isat right angles to the board. If the motor(or other load) is rated at 300 W, a 3 mmthick aluminium sheet of the same size asthe board is fixed above the board: at oneside directly to the heat sink and at the otherside via two spacers. Drill suitable holesin this sheet to retain access to the pre-sets.

In Fig. 6b, the IGBT is bent slightlyand mounted on the board with a (300 mm)


76 GENERAL INTEREST

wide piece of aluminium, bent at right an-gles, sandwiched between them. Makesure that none of the tracks is touched.Moreover, the aluminium angled sheetshould be at a distance of mm fromR35 and the tracks to K5. Use heat conductingpaste liberally. Next, screw a heat sink of52 K W 1 (SK04) to the aluminium.Finally, mount the NTC on the heat sinkas close as possible to the IGBT.

The finished board must be fitted in ametal enclosure, which allows at least3 mm space between it and the board.The enclosure must, of course, be earthedin accordance with safety regulations (inthe UK, this should be the mains earth)see Fig. 7.

Connect the open -circuit converter tothe mains and switch this on, whereuponthe relay should be actuated. Check thatthere is a voltage of about 340 V on C25.When the mains is switched off, this po-

O

O

O 0 0

0a

co

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00

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0 0 0 CM

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O 0 0 0 c,O 0 0 0 0 0 CM

O I g 0 0

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Fig. 7. The converter in its (earthed!) metal enclosure.

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1 -TO -3 -PHASE CONVERTER - PART 2 rig

+ R1 U S1 V T1 W R2 S2 T2 -940077-2-12

Fig. 8. How to fit the IGBT from International Rectifiers.

tential should disappear within 5-6 s.The board is designed for an IGBT

Type MP6750 from Toshiba. If this is dif-ficult to obtain, International Rectifiers'Type CPV363MF may be used. Since thisis not pin compatible with the Toshibamodule, some pins have to be linked to theboard with short lengths of wire as shownin Fig. 8.

If a Variac m (variable transformer) is avail-able, supply the mains via this and adjustit to give a potential of 270 V across C26.Adjust P7 to cause the level at pin 4 ofIC16d changes from high to low. Then, ad-just the Variac to give a potential of 360 Vacross C26 and adjust P6 to cause the levelat pin 8 of IC16c to change from low tohigh.

If a Variac is not available, measure thepotential across C26 and C35. Turn P6 untilthe voltage at its wiper is (Uc26/360) Uc35volts. Adjust P7 until the voltage at itswiper is (I/c26/270) Uc35 V. Remobve theVariac and connect the mains directly tothe converter.

If a temperature gauge is available,check that the thermal protection is ac-tuated when the temperature reaches80-85 °C.

Connect a three-phase motor to theconverter and switch on the mains. Themotor earth should be connected to the mainsearth (standard in UK). Set all poten-tiometers, other than P6 and P7, to thecentre of their travel and link K2 to K4.The motor should then gradually begin torun. Set the rotational speed with P5. If themotor switches off or on too quickly, thismay be remedied by varying P4 and P3 re-spectively. Finally, set P1 (motor runsclockwise) and P2 (motor runs anticlock-wise) as desired.

When the converter is used close to vi-brating parts (such as the motor itself), itis advisable to fix any parts that may beset into vibration (crystals, capacitors) inplace with heat -resistant glue.

When one of inputs 1-4 (pins 5-8 of K3and K4) is enabled and the mains isswitched on, the converter goes into an errorstate, indsicated by the lighting of D7 (whenthe output can not be made active). Thisstate is removed by earthing the relevant

input, whereupon D7 extignuishes andthe output may be actuated again.

A final note: since PWM signals areused, it is not possible to measure theoutput voltage with a multimeter. A true-r. m. s. meter or oscilloscope must be usedinstead. The voltage between two phasesmay be 220 V.

Parts list

Resistors:RI, R34, R37 = 560 tR2 = 82 52R3, R4= 2.2k52R5 -R12, R59 = 5.6 k52R13 -R17 = 3.3 IcQ

RI8 = 470 C2R19 = 330 QR20 = 680 QR21 -R23, R25 -R27, R53, R54, R56 =R24, R28 -R32 = 33 flR33, R36 = 0.18 SI, 5 WR36 = 120 QR38 = 12052R38 = NTC, 4.7 k52R39 = 270 QR40= 120k4R41 = 10 Ic52R42 = 470 SIR43 = 10 Id2R44= 1804R46 = 100 QR46, R48, R49, R55, R57 = 220 Id2R47= 180k4R50= 10k52, 5WR51 = 47 Q, 5WR52 = 1 li4R60, R61 = 470 Id/P1 -P4, P6, P7 = 25 Id/ presetP5 = 10 k52 linear potentiometer

Capacitors:

C27 = 15 nF, 1500 VC29, C31 = 22 pF, 16 V, radialC30 = 1000 pF, 25 VC32 = 470 pF, 25 V

Semiconductors:D1 = zener, 5.1 V, 400 mWD2 = zener, 6.2 V, 400 mWD3 -D6 = zener, 4.7 V, 400 mWD7 = LEDD8 -D10 = BYT11 or BYV36E

(1000 V, 150 ns)D11 D13 -D15 = 1N41448D12 = zener, 12 V, 400 mWD16 -D19 = FR606 (500 V, 5 A)B1 = rectifier bridge B250C1500B2 = rectifier bridge B40C1500Ti = BC547BT2 = BC337

Integrated circuits:ICI = 74HCT573IC2 = EPROM Order No. 946640-2*IC3 = TL7705A CP (Texas Instruments)IC4 = 800535 (Siemens)IC5 = GAL Order No. 946640-1*IC6-IC11 = PC923 (Sharp)IC12 = MP6750 (Toshiba) orCPV363 MF

(International Rectifier) see textIC13-1C15 = CNY17-4 (Siemens)IC16 = LM324IC17= 7812IC18 = 7805

Miscellaneous:JP1 = 2 -way jumperK1 -K4 = 2 -way terminal block,

pitch 5 mmK5 = 3 -way terminal block,

1.2 IcQ, pitch 7.5 mmK6, K7 = 2 -way terminal block,

pitch 7.5 mmX1 = crystal, 12 MHzF1 = fuseholder and 6.3 A slow fuseRef = relay, one change -over contact,

coil 12 VTr1 = mains transformer, 12 V, 3 A,

e.g. Velleman 1120038M (Maplin)Tr2 = mains transformers, 12 V, 1.5 A,

e.g. Velleman 1120018M (Maplin)1 off mains switch, 3 A, with indicator2 off heat sink, SK104 (37.5 mm high)t1 off heat sink SK68 (75 mm high) or

SW40/30 (100 mm high) with SK04-F(see text)

1 off metal enclosure, 00x00x00 mm1 off mains entry plug (3 A)1 off PCB Order No. 940077-1*

C1, C5, C23, C33, C34, C36, C37 = 100 nFC2, C3 = 27 pFC4 = 100 nFC6, C13 = 1 pF, 16 V, radialC7 -C11, C21 = 4.7 pF, 16 V, radialC12, C14 -C19, C24, C28, C35 = 10 pF, 16 V,

radialC20 = 470 pFC22 = 4.7 nFC25, C26 = 220 pF, 400 V, radial

Available as kit (PCB+EPROM+GAL)Order No. 940077-C

t Available from Dau (UK) Ltd70-75 Barnham RoadBarnham; West SussexEngland P022 OESTelephone +44 (0)1243 553 031


78 The publishers reserve the right to change prices without prior notification. Prices shown in this issue supersede those in previous issues. E. & O.E.

READERS SERVICESExcept in the USA and Canada, all orders, except for sub-scriptions and past issues (for which see below), must besent BY POST to our Dorchester office using the appropriateform opposite. Please note that we can not deal with PER-SONAL CALLERS, as no stock is carried at the editorial andadministrative office.Readers in the USA and Canada should send orders, exceptfor subscriptions (for which see below), to Old ColonySound Lab, Peterborough NH, whose full address is given onthe order form opposite. Please include shipping cost ac-cording to total order value. For surface delivery in the USA,if order is less than $50. include $3; $50+. $4. For Canadasurface, if less than US$50, include US$5; US$50+,

US$7.50. For air or other deliveries, please inquire. Pleaseallow 4-6 weeks for delivery.All other customers must add postage and packing chargesfor orders up to £25.00 as follows: UK and Eire £1.95; sur-face mail outside UK £2.45; Europe (airmail) £2.95: outsideEurope (airmail) £3.70. For orders over £25.00, but not ex-ceeding £100.00, these p&p charges should be doubled. Fororders over £100.00 in value, p&p charges will be advised.

SUBSCRIPTIONS & PAST ISSUESSubscriptions and past issues, if available, should be or-dered from Worldwide Subscription Service Ltd, Unit 4,Gibbs Reed Farm, Pashley Road, TICEHURST TN5 7HE,England. For subscriptions, use the order form on the oppo-site page.

Prices of past issues (except July/August and December), in-cluding postage for single copies, are £2.70 (UK and Eire);£3.00 (surface mail outside UK); £3.20 (air mail Europe);£3.95 (airmail outside Europe). Prices of past July/Augustand December issues, including postage for single copies,are £3.75 (UK); £4.00 (surface mail outside UK); £4.25 (air-mail Europe); and £5.00 (airmail outside Europe).

PAST ARTICLESPhotocopies of past articles are only available in combina-tion with the associated printed circuit board (see ProductOverview). The price of the photocopy is that of a past issue,which is sent in the first instance. If the relevant past issue isno longer available, you will receive a photocopy. Pleasestate 'plus photocopies' when ordering a printed circuitboard using the order form opposite.We regret that photocopies can not be supplied (1) sepa-rately, (2) if the relevant article does not describe a project ofwhich the printed circuit board is still available.

COMPONENTS

Components for projects appearing in Elektor Electronics areusually available from appropriate advertisers in this maga-zine. If difficulties in the supply of components are envis-aged, a source will normally be advised in the article. It

should be noted that the source(s) given is (are) not exclu-sive - other suppliers may also be able to help.

BOOKS

For book availability, see advertisement on page 81.

SHELF BOXElektor Electronics shelf box £2.95 $6.00

FRONT PANEL FOILS

PROJECT No. Price Price(£) (US$)

4MB printer buffer card 920009-F 8.25 16.50LC meter 920012-F 11.45 22.90Guitar tuner 920033-F 8.80 17.60NICAM decoder 920035-F 8.25 16.5012VDC to 240VAC inverter 920038-F 16.15 32.30Audio DAC 920063-F 10.00 20.00Digital audio/visual system 920022-F1 10.00 20.00

920022-F2 19.40 38.80920022-F3 28.80 57.60

1.2 GHz multifunctionfrequency meter 920095-F 13.80 27.60U2400B NiCd battery charger 920098-F 8.75 17.50Workbench PSU 930033-F 17.00 34.00Inexpensive phase meter 930046-F 17.25 34.50AF rms voltmeter 930108-F 17.25 34.50

PROJECT No.

- . 1

Multi -purpose Z80 card:

Price(£)

"

Price(US$)

BIOS (1 x EPROM 27128) 6121 15.30 30.60

1.2 GHz multifunctionfrequency meter(1 x 27C256) 6141 11.45 22.90

Digital audio/visual system(1 x 27C256) 6171 10.30 20.60

TV test pattern generator(1 x 27256) 6151 13.00 26.00

DiAV system. Package:1 x 27512; 2 x GAL; 1 x

floppy disk (MSDOS) 6181 30.50 61.00

PAL test pattern generator(1 x GAL 20V8-25) 6211 9.40 18.60

800535 assembler course(1 x EMON52 EPROM and1 x disk 1811) 6221 17.05 34.10

Watt-hour meter (1 x 27256) 6241 10.00 20.00

Four fold DAC (1 x GAL) 6251 10.75 21.50

Multipurpose display decoder(1 x 2764) 6261 11.50 23.00

Telephone -controlled switch(1 x 2764) 6271 14.50 29.00

Relative humidity meter (1 x 2764) 6301 14.50 29.00

535 card with EPROM emulator(1 x PAL and 1 x GAL) 6311 26.00 52.00

Copybit eliminator (1 x GAL 16V8and 1 x MACH110) 6321 42.25 84.50

RDS decoder (1 x 27C64) 6331 14.50 29.00

I2C tester (1 x GAL 6001) 6341 30.75 61.50Mains signalling system (1 x 27C64) 6371 13.25 26.50

8751 programmer (1 x 8751) 7061 46.40 92.80

Microcontroller NiCd charger(1 x ST62E15) 7071 10.00 20.00

Maxi micro clock (cock) 7081 11.50 23.00

Maxi micro clock (darkroom timer) 7091 11.50 23.00

Maxi micro clock (cooking timer) 7101 11.50 23.00Mini micro clock (clock) 7111 11.50 23.00Mini micro clock (darkroom timer) 7121 11.50 23.00

Mini micro clock (cooking timer) 7131 11.50 23.00

VHF/UHF TV tuner (1 x 87C51) 7141 25.75 51.50

Microntroller-driven UART(1 x ST62T10) 7151 17.25 34.50

PIC programmer (1 x PIC17C42and 1 x disk) 7161 52.75 105.50

MIDI swell pedal (1 x 27C64) 946635-1 13.75 27.50P.O.S.T. diagnostic card (PIC-1)946639-1 11.00 22.00

(PIC-2)946639-2 13.00 26.001 -to -3 -phase converter (GAL) 946640-1 12.25 24.50

(EPROM) 946640-2 15.75 31.50Solid-state disk (1 x 27256) 946641-1 23.50 47.00

TV line monitor (1 x PIC16C54) 946643-1 20.25 40.50

DISKETTES

GAL programmer (3 disks; upgrade;see June 1993 issue) 1701 11.15 22.30

Multi -purpose Z80 card 1711 7.65 15.30

Fuzzy Control One 1721 7.75 15.50

Pascal library for MMC 1751 9.70 19.40

Speech/sound memory 1771 7.65 15.30

PC -aided transistor tester 1781 7.50 15.00IR receiver and DTMF decoderfor 80C32 SBC 1791 9.00 18.00

800535 assembler course 1811 8.80 17.60

I2C opto/relay card 1821 7.65 15.30

Video digitizer for PCs 1831 14.50 29.00GAL programmer for Amiga 1841 11.00 22.00I2C alphanumerical display 1851 8.50 17.00

Philips preamplifier 1861 8.50 17.00GAL programmer (excl. OpalJr. disks) 1881 10.75 21.50Precision clock for PCs 1871 8.50 17.00X2404 -to -8751 interfacing 1891 8.50 17.00

RC5 software emulation 1901 10.75 21.50Mains signalling system 1911 9.75 19.50SIM - an 8051 simulator 1931 34.25 68.50800535 SBC extension 1941 9.75 19.50Small loop antennas 1951 10.75 21.50800535 SBC I2C display 946197-1 9.75 19.50PIC programming course 946196-1 9.75 19.50RC5 transmitter with 800535 946199-1 9.75 19.50

Debugging 8031/8051 micro -controller systems 946203-1 11.50 23.00ispStarter kit from Lattice 946204-1 9.75 19.50

PROJECT No. Price Price(C) (OSP

PRINTED CIRCUIT BOARDS

Printed circuit boards whose order number is followed by aC are only available in combination with the associated soft-ware item, and can not be supplied separately. The indicatedprice includes the software.

JUNE 1994800535 SBC extension 940025 19.75 39.50

12C bus booster 940057 7.25 14.50

RS485 interface 940035 6.25 12.50

Fuel consumption monitor 940045 6.00 12.00

Intelligent EPROM eraser 940058-1 9.00 18.00

JULY/AUGUST 1994General purpose IR volumecontrol 930099 9.00 18.00

IR controlled switch 936066 9.75 19.50

MIDI swell pedal,incl. EPROM 946635 940019-C 26.75 53.50

Charge meter 940033 5.75 11.50

Water softener 944011-1 6.00 12.00

Joystick -to -mouse adaptor 944040-1 7.00 14.00

Discrete preamplifier 944063-1 8.50 17.00

Centronics I/O interface 944067-1 8.75 17.50

80C451 controller board 944069-1 15.00 30.00

Robust AF power amp 944075-1 9.75 19.50

PC over -temperature alarm 944076-1 4.25 8.50

1-4 MByte SIMM adaptor 944094-1 15.50 31.00

Optical doorbell 944080-1 6.25 12.50

PIC experimenting board 944105-1 17.75 35.50

RC5 transmitter with 800535(incl. disk 946199-1) 944106-C 13.00 26.00

SEPTEMBER 1994

Switchable a.c. supply 934004 6.50 13.00

Anemometer & flow meter 940017 6.25 12.50

Compact frequency meter 940051-1 9.00 18.00

Revolution counter 940045-1 6.00 12.00

940068-1 5.50 11.00

OCTOBER 1994Motive -battery charger 940083-1 7.25 14.50

Integrated AF amplifier 936062-1 9.50 19.00

936062-2 28.25 56.50

Tester for IR remote control 940084-1 6.50 13.00

In -car audio amplifier (1) 940078-1 14.00 28.00TV line monitor (incl.PIC 946643-1) 940065-C 26.25 52.50

NOVEMBER 1994Single -wire communication 940055-1 4.00 8.00

In -car audio amplifier (2) 940078-2 30.25 60.50

Solid-state disk (incl.EPROM 946641-1) 940085-C 47.50 95.00

Simple capacitance meter 940091-1 10.00 20.00

DECEMBER 1994

In -car audio amplifier (3) 940078-2 30.25 60.50

RF immune power supply 940054-1 9.00 18.00ispStarter kit from Lattice 940093-C 21.50 43.00Proximity detector 940108 Not available30m QRP CW transmitter 944020 Not availableTemperature. protection forhigh -power resistive loads 944014 Not available

Electret microphone fortelephone mouthpiece 944003 Not availableCurrent probe 944093 Not availableStand-alone copybit eliminator 944052 Not available

JANUARY 1995Mini Audio DAC 940099-1 14.75 29.50

1 -to -3 -phase converter (incl.GAL & EPROM 946640-1 and -2) 940077-C 52.75 105.50P.O.S.T. diagnostic card (incl.GALs 946639-1 and -2) 950008-C 29.25 58.50Self -loading EEPROM typeX88064 SLIC 940116-1 8.25 16.50

Debugging 8031/8051 micro -controller systems (incl. disk946203-1) 940117-C 15.00 15.00

Quasi -analogue clockwork 930024 37.25 74.50

A list of all PCBs, software products and front panels available through the Readers Services is published in theMarch, June, September and December issues of Elektor Electronics


x79

x

Please send this order form to *

Elektor Electronics (Publishing)P.O. Box 1414Dorchester DT2 8YHENGLANDTel. (01305) 250995Fax (01305) 250996

* USA and Canada residents only: use $ prices, and send orderform to:Old Colony Sound Lab, P.O. Box 243, Peterborough,NH 03458.Tel. (603) 924-6371, 924-6526, Fax: (603) 924-9467

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80

TERMS OF BUSINESSHOW TO PAYUnless you have an approved credit accountwith us, all orders must be accompanied by thefull payment, including postage and packingcharges as stated on page 70, section I.

Payment may be made by cheque drawnon a London clearing bank (but see para. 4below), postal order, VISA, ACCESS, MAS-TERCARD or EUROCARD (when paying bycredit card, the order must go to the card-holder's address). Do not send cash throughthe mail. Cheques and postal orders should becrossed and made payable to `ElektorElectronics (Publishing)'.

Payment may also be made by direct trans-fer from a private or business Giro account toour Giro Account No. 34 152 3801 by com-pleting and sending to the National GiroCentre, in a National Giro postage paid enve-lope, a National Giro transfer/deposit form. Donot send Giro transfers direct to us, as this willdelay your order.

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If you pay by Bankers' sterling draft, makeclear to the issuing bank that your full nameand address MUST be communicated to theLondon clearing bank.

Our bankers are National WestminsterBank, 49 South Street, DORCHESTER,

r

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DELIVERYAlthough every effort will be made to dispatchyour order within 2-3 weeks from receipt ofyour instructions, we can not guarantee thistime scale for all orders.

RETURNSFaulty goods or goods sent in error may be re-turned for replacement or correction, but notbefore obtaining our consent. All goods re-turned should be packed securely in a paddedbag or box, enclosing a covering letter statingthe dispatch note number. If the goods are re-turned because of a mistake on our part, wewill refund the retum postage. Goods returnedfor refund must be in resaleable condition andwill be subject to a 10% handling charge witha minimum charge of £2.50.

DAMAGED GOODSClaims for damaged goods must be received atour Dorchester office within 10 days (UK); 14days (Europe) or 21 days (all other countries)from the date on our "Recorded Delivery" slip.

CANCELLED ORDERSAll cancelled orders will be subject to a 10%handling charge with a minimum charge of£2.50.

PATENTSPatent protection may exist in respect of cir-cuits, devices, components, and so on, de-scribed in our books or magazines. ElektorElectronics (Publishing) do not accept respon-

sibility or liability for failing to identify suchpatent or other protection.

COPYRIGHTAll drawings, photographs, articles, printed -circuit boards, EPROM5, and cassettes publishedin our books or magazines (other than in third -party advertisements) are copyright and maynot be reproduced or transmitted in any formor by any means, including photocopying andrecording, in whole or in part, without the priorpermission of Elektor Electronics (Publishing)in writing. Such written permission must alsobe obtained before any part of these publica-tions is stored in a retrieval system of any na-ture.

Nothwithstanding the above, printed -cir-cuit boards may be produced for private andpersonal use without prior permission.

LIMITATION OF LIABILITYElektor Electronics (Publishing) shall not be li-able in contract, tort, or otherwise, for any lossor damage suffered by the purchaser whatso-ever or howsoever arising out of, or in connex-ion with, the supply of goods or services byElektor Electronics (Publishing) other than tosupply goods as described or, at the option ofElektor Electronics (Publishing), to refund thepurchaser any money paid in respect of thegoods.

LAWAny question relating to the supply of goodsand services by Elektor Electronics(Publishing) shall be determined in all respectsby the laws of England.

October 1994

Annual subscription rates (1995)

United Kingdom £ 28.00Rest of the world (surface mail) £34.00AIRMAILEurope & Eire £ 35.00USA & Canada $59.00Middle East & North Africa £44.00Central & southern Africa £4400Central & South America £4400Australia & New Zealand £46-00Far East & South Pacific regions £46-00

Payment may be made by cheque in sterling drawnon a London clearing bank (but see below), postalorder, VISA, ACCESS, MASTERCARD or EUROCARD (inwhich case the subscription must be sent to the card-holder's address) or by direct transfer to our GiroAccount no. 34 152 3801. Do not send cash through themail. Cheques and postal orders should be made payableto `Elektor Electronics Publishing'. Giro transfersshould be made by completing and sending the appropri-ate transfer/deposit form to the National Giro Centre(UK) or to your national Giro Centre.

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The standard subscription order period is twelvemonths. If a permanent change of address during yoursubscription period means that copies have to be dis-patched by a more expensive service, no extra chargewill be made. Similarly, no refund will be made, nor ex-piry date extended, if a change of address allows the useof a cheaper service.

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Please note that new subscriptions take about fourweeks from receipt of order to become effective.

Cancelled subscriptions will be subject to a charge of25% (twenty-five per cent) of the full subscription priceor £7.50, whichever is the higher, plus the cost of any is-sues already dispatched. Subscriptions cannot be can-celled after they have run for six months or more.

Our bankers are National Westminster Bank PLC,Sorting Code 60-07-01, 49 South Street, Dorchester,Dorset, England DT1 1DW. Our account number is6966 3440.

L

October 1994J


81

SWITCHBOARDSwitchboard allows all PRIVATE READERS ofElektor Electronics one FREE advertisementof up to 108 characters, including spaces,commas, numerals, etc., per month,

Write the advertisement, which MUSTrelate to electronics, in the coupon on thispage; it MUST INCLUDE a private telephonenumber or name and address; post officeboxes are NOT acceptable.

Elektor Electronics (Publishing) can not ac-cept responsibility for any correspondence ortransaction as a result of a free advertisementor of any inaccuracy in the text of such an ad-vertisement.

Advertisements will be placed In the orderin which they are received.

Elektor Electronics (Publishing) reservethe right to refuse advertisements withoutgiving reasons or without returning them.

FOR SALE. PIC programmer (ElektorElectronics, March 1994) £100.00 o.n.o..Please ring Mike Mee in New Zealand +6403 7500 016 (mornings GMT).

FOR SALE. Mini 12 V bulbs with 25 cm leads;10 for £1.00. Send cheque/PO to M. Knight,10 Daniel Road, Mancetter, Atherstone,Warwickshire, England CV9 1 PA

WANTED. Manual for Rohde & SchwarzLRU610D Inductance meter. Loan/purchse;reasonable costs met. Please write to P.Redway, 169 Ballards Walk, Basildon, Essex

IF AN ADVERTIS IN PRINT,

IS ITPROPER?Most advertisements are

perfectly proper. Afew are not.The Advertising Standards

Authority not only monitorsover 850 advertisements everymonth, it ensures compliancewith the rules in the strictCode of Advertising Practice.

So when you questionan advertiser, they have toanswer to us.

To find Out more about therole of the ASA, please write toAdvertising Standards)

Authority.Dept X, Brook House.

lbrrington Place,London WCIE 711N.

SATills spare Is donated in the Interestsof high standards In athertIsements.

SS15 5JU.

FOR SALE. Racal RA17 receiver, £130; weathersat receiver/frame store YU3UMV, £200.Please phone (01884) 32388.

FOR SALE. Elektor 8051 SBC computer withextension board, incl. complete Elektor course,two LCD displays and small 8051 stand-alonecomputer, £60.00. Phone Jonathan on(01905) 358 742 (evenings).

FOR SALE. Thandar SC110A portable scope,£125. Also Fluke 87 true-rms multi meter,£125. Both in Al condition. Phone (0181)423 2224.

FOR SALE. RF Signal generator, PrecisionGold, still boxed, £45. Also Marconi univer-sal brridge TF2700, solid-state, with manual,£25. Phone (01272) 407 599 (evenings).

FOR SALE. Oscilloscope Farnell DTV60, 3 -channel, 8 -trace, 60 MHz, with manual, probesand case. Current model, fabulous condition,£365. Phone Peter on (01272) 407 599.

WANTED. Formant information or similarsynthesizer OTA, VCO circuit diagram, etc.Also UA726C or equivalenmt. Buy for cashor swap. Phone Chris on (01235) 534 152.

FOR SALE. Twenty 87P50 microcontrollersuse piggyback 2716/32 in place of 8048/49/50,£15 each. Phone (0114) 239 274 (evenings).

FOR SALE. HF, VHF satellite communicationequipment of marine. Write to T. Dasan,FA111 Alembic Colony, Baroda-3, Gujarat,

Send this coupon toElektor Electronics (Publishing)

P.O. Box 1414Dorchester DT2 8YH

England

B ock capitals p ease - one character to each box

ELEKTOR ELECTRONICS 01/95

Name and address MUST be given

India.

Books from Elektor Electronics (Publishing)

The following books are currently available:How to build your own Electronic Test Instruments £15.95 $29.50Short course 8051/8032 Microcontrollers and assembler £9.95 $18.50SMT Projects £ 9.95 $18.50301 Circuits £9.95 $18.50302 Circuits £9.95 $18.50303 Circuits £10.95 $20.25304 Circuits E12.95 $23.95305 Circuits £14.95 $27.70Microprocessor Data Book £10.95 $20.25Data Sheet Book 2 £9.95 $18.50Data Book 3: Peripheral Chips £10.95 $20.25Data Book 4: Peripheral Chips £10.95 $20.25Data Book 5: Application Notes £10.95 $20.25All prices are exclusive of p&p, for which see page 78

How to order:UK and Overseas private customers (NOTin USA and Canada) from:Elektor Electronics (Publishing)PO Box 1414 Dorchester, England DT2 8YHTelephone (0305) 250 995Fax: (0305) 250 996

UK and Overseas bookshops, schools,colleges, universities and bulk orders

(NOT in USA and Canada) from:Gazelle Book Services LtdFalcon House, Queen Square, Lancaster,England LA1 1RNTelephone (0524) 68765Fax: (0524) 63232

USA and Canada ONLY from:Old Colony Sound - please see order formon page 79 for details


82

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L.F. HANNEYYour electronic component

specialist forAvon, Wilts & Somerset.77 Lower Bristol Road,

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AAGE NIELSEN1 Sortedam DosseringenDK-2200 Copenhagen,

Denmark,Telephone 01 39 30 10

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MK KNJIGARNASlovenska 29

LjubljanaSlovenia

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THE ELECTRONIC SHOPElectronic components, test

equipment, telephoneaccessories, computer

accessories, microphones,disco lighting, speakers, turntables, mixers, meters, stylus.

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HELMHOLT ELEKTRONIKFarvevej 2

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Electronic componentspecialists. Amateur radio

equipment.13 St. Benedict Street,

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INEL Co.P.O. Box 1397

JL. Hariang Banga No. 3Bandung 40116

IndonesiaOMNI ELECTRONICSStock a wide range of

electronic components.174 Dalkeith Road,

Edinburgh EH16 5DX,Telephone 0131 667 2611

BEBEK ELECTRONICSHirsimetsantie 26SF -15200 Lahti 11

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AP ElectronicsAudon ElectronicsBadger BoardsB K ElectronicsBluebird ElectronicsBull ElectricalCirkit DistributionCricklewood ElectronicsCrossware ProductsDisplay ElectronicsElectromailElektor ElectronicsESR Electronic ComponentsExpress ComponentsHart Electronic KitsHitex (UK) LtdInstrutekMaplin Electronic SuppliesMicroAmpsMilford InstrumentsNiche SoftwareNumber One Systems LtdPico Technology LtdPOWERwareQuantek ElectronicsRobinson MarshallSmart CommunicationsSpeaker BuilderStewart of ReadingSuma Designs

INDEX OF ADVERTISERS

1940471950206327405141

43, 49, 814

62725017

Back cover71632731486850

Inside back cover35717769

Those EngineersTsien (UK) LtdUltimate TechnologyViewcom Electronics

1157

Inside front cover12, 13

ADVERTISING SPACEfor the February 1995 issue may be reserved

not later than8 December 1994 by

Elektor Electronics (Publishing)Advertisement Office3 Crescent Terrace

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Telephone (01242) 510 760; Fax (01242) 226 626

to whom all correspondence, copy instructions andartwork should be addressed.

Focus article in the February 1995 issue will beCOMPUTER -AIDED DESIGN of

printed -circuit boards and circuit diagrams



File Edit Circuit Window Help Bode

"Electronics Workbench

is the best simulator to

design and verify circuits."Gordon MacDonald

Production Engineer Technician

6m r-rf.ca3 pi Parts

6mt -rfiMI

E6n t t

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c1_______sja 1I

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Electronics5 Workbench

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Electronics Workbench is a highlyproductive bench where you design andverify circuits in a fraction of the time.Connections are always perfect.Wiresroute themselves. And the simulatedcomponents and test instruments workjust like the real thing.

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It's faster than building with actualcomponents because you changeconnections and component valuesinstantly. And since the simulatedcomponents are free, you don't need toreplace burnt -out parts or keep anextensive inventory. The result: You saveprecious time and money. Guaranteed!

The standard for simplicity and power forover six years, Electronics Workbench is themost popular tool of its kind. It has gainedworldwide acdaim as the ideal complementto any test bench. Fact: Over 90% ofour customers recommend it totheir friends and colleagues.

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