dieu khien plc

8/2/2019 Dieu Khien PLC

1/29

iu khin tc ng c bng my tnh

L thnh sn http://www.ebook.edu.vn 1

Phn m u

My vi tnh ngy cng gi mt vai tr quan trng trong cc lnh vckhoa hc k thut v cuc sng. Do s pht trin mnh m c v mt phn

cng cng nh phn mm. Cng v vy vic ng dng my tnh vo k thut

o lng em li nhng kt qu rt to ln. Vi cc thit b o lng khi

em ghp ni ni my vi tnh c chnh xc cao, thi gian thu thp d liu

ngn, nhng iu quan trong nht l mc t ng ho trong cng vic

thu nhp cng nh x l s liu t cc kt qu o rt cao ngay c trong cng

vic thng k hay in n kt qu . Ngoi ra trong nhiu trng hp vi mi

trng lm vic nh m, nhit ...Khng ph hp vi con ngi th lc

ny cc h o s c ghp ni vi my tnh l khng th thay th c.

Trong ti ny l nhng c gng bc u xy dng h o lng

iu khin ghp ni vi my tnh thng qua cng COM .


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Phn l thuyt


3/29



I . o lng v ghp ni vi my tnh qua

cng RS- 232

H1. S khi n gin ca mt h o lng v ghp ni

vi my tnh qua cng RS - 232.

S khi n gin ca mt h o lng v ghp ni vi my tnh

qua cng RS- 232 nh hnh 1. S liu t u o l analog s c a ti

card ghp ni card ghp ni ny s c b bin i A/D v sau n sc bin i thnh tn hiu chun ca RS-232. Tc l mc +3V n +12V

tng ng vi mc 0 v -3V n -12V tng ng vi mc 1. a d liu

vo PC qua cng COM th ta phi c phn mm nht qun gia card ghp

ni v cng COM v mt tc , cng mt format thng tin SDU.

II. Thng tin ni tip

1. Thng tin ni tip vi chun RS- 232Cng ni tip RS- 232 l loi giao din ph bin, rng ri nht. Ngi

dng my PC cn gi cc cng ny l COM1 v COM2. Vi COM2 t

do cho cc ng dng khc. Ging nh cng my in v cng thng qua card

ghp ni qua slot m rng th cng ni tip RS- 232 cng c s dng mt

Cardghp ni

COM

u o


4/29



cch ht sc thun tin cho cc mc ch o lng v iu khin cng nh

khi c mt ng dy lin lc hay mt knh thng tin th n c th c rt

nhiu ng dng nh truyn vn bn qua modem hay fax.

Vic truyn d liu qua cng RS- 232 c tin hnh theo cch ni

tip, ngha l cc bt d liu c gi i ni tip nhau trn mt ng dn.

Trc ht, loi truyn ny c kh nng dng cho nhng khong cch ln

hn, bi v cc kh nng gy nhiu l nh ng k hn khi dng mt cng

song song. H thng tin trao i ni tip c thc hin theo cc phng

thc :

a cng: s liu ch c gi theo mt hng Bn song cng: s liu c gi theo hai hng nhng ti mi thi

im th ch c th gi i theo mt hng

Song cng: s liu c gi theo hai hng thng tin ni tip cphn lm hai loi:

+ Thng tin ng b

+ Thng tin khng ng b

Trong thng tin khng ng b (di b), mt t (hay mt cm t) th

c truyn hay thu theo tng khung mt v khung gi l SDU (serial

data unit). Mt khung bao gm:

Mt bt start 5,6,7,8 bt d liu 1 bt pht hin li Bt stop (1,1.5 hoc 2)

y bt pht hin li l dng bt chn-l

2. Chun ghp ni RS- 232


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Cng ni tip RS-232 khng phi l mt h thng bus, n cho php

d dng to ra lin kt im-im gia hai my cn trao i thng tin vi

nhau. Mt thnh vin th 3 khng th tham gia vo cuc trao i thng tin

ny.

Chn(loi 9

chn)

Chn(loi

25 chn)

Chc nng

1

2

34

5

6

7

8

9

8

3

220

7

6

5

4

22

DCD(Data carrier delect) Li vo

RxD(Receiver data) Li vo

TxD(Transmit data) Li raDTR(Data terminal ready) Li ra

GND(Ground)

DSR(Data set ready) Li vo

RTS(Request to send) Li ra

CTS(clear to send) Li vo

RI(Ring Indicator) Li vo

H . 2 Sp xp chn ca cng ni tip my tnh PC

T hnh 2 ta thy cm RS-232 c tng cng 8 ng dn v mt

ng t. Trn thc t c hai loi phch cm 9 v 25 chn, c hai loi ny

u chung c im lm vic.


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Vic truyn d liu xy ra trn 2 ng dn RxD v TxD. Qua chn

TxD, my tnh gi d liu ca n n my kia. Trong khi th my tnh

nhn cc d liu ti chn ni RxD. Cc tn hiu khc ng vai tr nh l

nhng tn hiu h tr khi trao i thng tin v v th khng phi trong mi

ng dng u dng c.

Vic truyn d liu : Mc tn hiu trn chn ra RxD tu thuc vo

ng dn RxD v thng thng nm trong khong -12V n +12V. Cc

bt d liu c gi o ngc li. Mc in p i vi mc high nm gia

-3V -12V v mc Low nm gia +3V +12V. Trn hnh 3 m t mt

dng d liu in hnh ca mt byte d liu trn cng ni tip RS- 232.Khi trng thi tnh trn ng dn c in p -12V. Mt bt khi

ng (bt start ) s m u vic truyn d liu. Tip l cc bt d liu

ring l s n, trong nhng bt gi tr thp s c gi trc tin. Con s

ca cc bt d liu thay i gia 5v 8 bt. cui ca dng d liu cn mt

bt dng (stop bt), t tr li trng thi li ra (-12V)

Bng tc baud ta thit lp tc truyn d liu v cc gi tr thng

thng l 300; 600; 1200; 2400; 4800; 9600 v19200 baud. V y k

hiu baud tng ng vi s bt c truyn trong mt giy. T ta thy

rng c mt bt start v bt stop c gi cng bt d liu. Nh vy ta c th

bit c tc cc i ca d liu c truyn nh vy vi mi byte c

10 bt c gi. Vi tc 9600 baud cho php truyn nhiu nht l 960

byte mi giy. Qua cch tnh ny ta thy mt nhc im khng nh ca

cng truyn ni tip l tc truyn d liu b hn chCn vi vn na l khun mu (Format) truyn d liu cn phi

c thit lp nh nhau c hai bn (bn gi v bn nhn). Cc thng s


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truyn c th c thit lp trn cc my PC bng cc cu lnh trn DOS.

Ngay c trn Window cng c chng trng ring s dng n.

Khi cc thng s truyn d liu nh: tc baud, s bt d liu, s

bt dng, bt chn l (parity) c th c thit lp mt cch rt n gin. S

trao i ca ng dn tn hiu y cc ng dn tn hiu ring bit cng

Start bt Stopbt

12V LOW

D0 D1 D2 D3 D4 D5 D6 D7

-12V HIGH

104 s

1,04 ms

H.3 dng d liu trn cng RS- 232 vi tc 9600 baud

cho php trao i qua cc a ch trong my tnh PC. Trong trng hp ny,

ngi ta thng s dng nhng vi mch c mc tch hp cao c th

hp nht nhiu chc nng trn mt chip. My tnh PC thng c h thu pht

khng ng b vn nng UART (Universal Asychronous

Receiver/Transmitter) iu khin s trao i thng tin gia my tnh v

cc thit b ngoi vi. Ph bin nht l vi mch 8250 ca hng NSC hoc cc

th h tip theo chng hn nh 16C55O. B USAT ny c 10 thanh ghi

iu khin tt c cc chc nng ca vic nhp vo v xut ra d liu theo

cch ni tip- Bus Interface: giao din bus

- Transmitter Hold Register: thanh ghi d truyn

- Transmitter Shift Register: thanh ghi dch truyn


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- Interface Control Baud Generator: my pht iu kin tc truyn

s liu baud

- SDU logic: mch logic SDU

- Serial data : S liu ni tip .

Truyn 1 SDU c s nh sau:

Thu 1 SDU c s nh sau :

- Bus Interface: giao din bus

-Receiver Buffer Register: thanh ghi m s liu thu

BusInterface

Interface Control Baud Generator

TransmitterHold Register

SDUlogic

TransmitterShift Register

Hnh 4 : S pht SDU

Serial data

Bus

Interface

Interface Control Baud Generator

ReceiverBuffer

Register

SDUlogic

ReceiverShift Register

H.5 S thu SDU

Serial data


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-Receiver Shift Register: thanh ghi dch truyn-Interface Control Baud Generator: my pht iu kin tc truyn

s liu baud

-SDU logic: mch logic SDU-Serial data : S liu ni tip .

3. B thu pht khng ng b vn nng USAT 8250

B x l 8250 l mt vi mch dng bin i thng tin song song

thnh ni tip c lp trn bn mch chnh ca PC nhm phc v cho trao

i thng tin ni tip gia PC v cc thit b ngoi vi qua cc cng I/O vi

cc u cm vt l (l cc cng COM)

3.1. S chn

Vi mch 8250 c 40 chn vi cc tn hiu c bn nh hnh 6. Con s

ch s chn ca 8250 chia thnh cc nhm sau:

a) Nhm a chCS0, CS1, CS2: chn vi mch t b gii m An n A3, tc l chn tt

c cc a ch ca cc thanh ghi ni

A0, A1, A2 : chn 10 thanh ghi ni c th ca 8250 xc nh thanh

ghi no CPU ang tham nhp cho c hoc vit

CSOUT (chip select out): mc cao, cho bit VXL chn vi mch

bi CS0, CS1, CS2.

ADS (address select): mc thp, ch th rng tn hiu a ch v cc

tn hiu s liu.

b) Nhm tn hiu s liuD0 n D7: ng bus s liu vo ra hai chiu vi VXL

- SIN (Serial in) : li vo ni tip ca s liu vo t thit b ngoi


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H.6 S chn ca 8250

-------

-SOUT (serial out): li ra ni tip ca s liu a ra thit b ngoi-WR (DOSTR ), WRC (DOSTR) hay DOUTS , DOUTS: cc li vo lnh

ghi ca VXL , VXL ghi s liu hoc li iu khin vo cc thanh ghi nica 8250.


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-RD (DISTR ), RD(DISTR) hay DINS , DINS cc li vo ca lnh cca VXL , VXL c s liu hoc t iu khin ca cc thanh ghi ni ca

8250

- DDIS mc thp ch VXL ang c s liu t 8250

c)Nhm tn hiu nhp-XTAL1, XTAL2 : cc li vo ca tinh th thch anh-RCLK (Receiver clock) : li vo xung ng h 16 ln tc baud-Baudout : li ra xung nhp c tn s bng 16 ln tc baud

d) Nhm iu khin modem-DTR (Data terminal Ready) : sn sng ca terminal cho s liu-DSR (Data set Ready) : sn sng ca b s liu-RTS (Request to send) : yu cu gi-CTS (Clear to send) : xo gi-DCD (Detect Carrier Data ): Pht hin sng mang s liu-RI (Ring Indicator) : ch th chung

e) Nhm iu khin khc-iu khin ngt

INTR : yu cu ngt 2OUT : dng trong my vi tnh PC lm tin hiu cho php ngtchnh qua cng logic

1OUT : li ra t iu khin modem, cho ngi s dng-Xo Vcc, GND, Reset

f) Ngun nui


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S mc ca mt 8250 vi VXL v modem, nh hnh 7. S dng

xung nhp ca my pht xung ni (li ra Baudout ni vi li vo RCLK.

Mt s li vo khng s dng CADS, DOSTR, CSO,CS1 c ni vi mc

logic 0 v 1 nh hnh v.

H.7 S mc v tn hiu ca 8250


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Address DecoderControl Logic

8250 Control Logic

PCInterface

Databusbuffer

Receiver

buffer re isterData formatre ister

Divisor latchre ster LDB

Divisor latchre ister MDB

Modemcontrol re ister

Status registermodem

Interrup IDre ister

Transmitterhold re ister

Serializationstatus re ister

Interrupactivation

Scratch padre ister

Baud

IRQcontrollogic

Receiver shift

re ister

Receivercontrol

Modemcontrollogic

Transmittercontrol

Transmittershift ri ister

SIN

SCLK

BaudOut

32 RTS36 CTS

33 DTR37 DSR

38 DCD39 RI 34 1OUT

INTRPT

Sout

31 2OUT

Hnh 8 : S khi ca UART 8250


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3.2. S khi

Vi mch 8250 c chia thnh cc khi chc nng sau :

a) Khi iu khin ngt- Logic iu khin ngt- Thanh ghi nhn dng ngt

b) Khi my pht c-My pht baud-Cc cht b chia tn s, byte thp, cao (LS) v (MS) pht tn smun pht-iu khin v nh thi my thu, khi ny c nhim v pht xungnhp cho 8250 v theo chng trnh

c) Khi iu khin modem gm-Logic iu khin modem-Thanh ghi iu khin modem-Thanh ghi trng thi modem

d) Khi thu gm-Thanh ghi dch my thu-B ghi m my thu

e) Khi pht gm-Thanh ghi m my pht (B n nh my pht)-Thanh ghi dch my thu

f) Khi iu khin chung gm-thanh ghi dng s liu-thanh ghi trng thi ni tip


15/29



3.3. Cc thanh ghi UART 8250

a ) Thanh ghi iu khin ng truyn (line control register, LCR)

Thanh ghi iu khin ng truyn cn c tn l thanh ghi nh dng

khun d liu v n quyt nh ti khun dng ca d liu truyn trn ng

dy. Vi thanh ghi LCR th vic quy nh s bt stop khng nhng ph

thuc vo gi tr bt D2 m cn ph thuc di m k t

D7 D6 D5 D4 D3 D2 D1 D0

DLAB SBCB SP EPS PEN STB WLS1 WLSO

- Bt 1-0 : Cho php chn di t00 = 5 bt / k t

01 = 6 bt / k t

10 = 7 bt / k t

11 = 8 bt / k t

- Bt 2 : Chn s bt stop.0 : 1 bt

1 : 1.5 bt

2 bt

- Bt 3 : Cho php to / kim tra parity1 : cho php

0 : cm v ng thi bt 4 khng c tc dng

- Bt 4 : Chon to / kim tra parity chn l.1 : parity chn

0 : parity l

- Bt 5 : o parity.


16/29



1: o parity.0 : khng hot ng

- Bt 6 :iu khin gin on.1: buc Sout = 00 : khng hot ng

- Bt 7 : Bt truy nhp s chia dng m rng lnh cho cc thanh ghi chtb LSB,MSB.

0 : c / ghi my thu , pht

1 : cht chia tc

b ) Thanh ghi m gi pht (transmitter holding register THR)K t cn pht i phi c ghi t CPU vo thanh ghi ny trong khi

bt DLAB =0. Sau khi truyn 8250 ly k t t dy truyn, ng khung

cho n nh nh v a tng bt ra chn Sout

c ) Thanh ghi m thu ( Receiver bufer register RBR)

Khi 8250 nhn c mt k t qua chn SIN, n s tho b khung

cho k t v gi k t ti thanh ghi m thu CPU c. CPU ch c c

k t trong thanh ghi ny khi bt DLAB = 0.

d ) Thanh ghi cho php to yu cu ngt (Interrupt enable register IER)

Thanh ghi ny dng cho php cm cc nguyn nhn gy ngt khc

nhau trong khi mch 8250 hot ng, c th tc ng c ti CPU thng

qua chn INTRPT ca USRT

D7 D6 D5 D4 D3 D2 D1 D0

0 0 0 0 MODEM RLINE TxEMTY RxRDY

Bat 0: Cho php ngt khi m thu y khi = 1

Bt 1 = 1: Cho php gy ngt m gi pht rng.


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Bt 2 = 1: Cho Php cc tn hiu trng thi ng dy thu gy ngt.

Bt 3 = 1: Cho php cc thay i trng thi ca modem gy ngt.

Bt 4 n 7 : C gi tr l 0

e ) Thanh ghi nhn dng ngun yu cu ngt (Interrupt identification

register IIR)

Thanh ghi nhn dng ngt (ch c ra) cha m mc u tin cao

nht ca yu cu ngt (ti chn INTRPT ca 8250) ng ch c phc v.

Do vy khi cn x l cc yu cu ngt theo kiu thm d, CPU ch cn c

bt ID0 ca thanh ghi ny bit l c yu cu ngt v kim tra cc bt ID2

n ID1 xc nh c ngun gc ca yu cu ngt.D7 D6 D5 D4 D3 D2 D1 D0

0 0 0 0 0 ID2 ID1 ID0

Bt 0 : 0 : c yu cu ngt cn x l

1 : khng c yu cu ngt cn x l

Bt 2 : 1 : 00 : Trng thi modem

01 : m gi pht rng

10 : m thu y

11 : Trng thi ng thu

f ) Thanh ghi iu khin modem (modem control register MCR)

Thanh ghi ny cn c gi l thanh ghi iu khin cc tn hiu ra

ca modem bi v n cho php ta iu khin cc tn hiu ti cc chn DTR

v RTS ca mch UART.D7 D6 D5 D4 D3 D2 D1 D0

0 0 0 LOOP OUT2 OUT1 RTS DTR


18/29



Bt D0 = DTR = 1 ta c th iu khin tn hiu ti chn DTR ca

mch 8250 t mc tch cc thp bo UART sn sng lm vic

Bt D1 : RTS =1 ta c th iu khin tn hiu ti chn RTS ca mch

8250 t mc tch cc thp bo UART sn sng pht k t.

Bt D2 : Kch hot OUT1 khi = 1

Bt D3 : Kch hot OUT2 khi = 1

Bt 4 = 1 Cho php iu khin mch 8250 lm vic ch ni vng

cc b kim tra phn hi cc b.

Khi D4 = 1 th Sout = 1

- SIN ca b phn thu b c lp- Li ra ca thanh ghi dch ca b phn pht c ni trc tip

n li vo ca thang ghi dch ca b phn thu

- Cc chn iu khin vo ca modem ( DSR , CTS ,RI ,DCD )khng c ni ra ngoi m c ni bn trong mch vi

cc chn iu khin ra ca modem ( DTR , RTS , 2OUT , 1OUT ).

Cch ghp ni ny dng kim tra 8250 bng cch ghi vo thanh

ghi m s liu pht, s liu li c ghi vo thanh ghi m s liu

thu.

g ) Thanh ghi trng thi modem.( modem status register MSR)

Thanh ghi ny cn c gi l thanh ghi trng thi vo t RS- 232 v

n cho bit trng thi hin thi ca cc tn hiu iu khin modem t ng

dy.

D7 D6 D5 D4 D3 D2 D1 D0DCD RI DSR CTS DCD RI DSR CTS


19/29



Du ng trc cc tn hiu l ch ra rng trong khi 8250 hot

ng, nu c s thay i ca cc tn hiu th cc bt tng ng s c

lp, ring i vi tn hiu RI th RI ch bo rng s thay i t mc thp

ln mc cao

Bt D2 = 1 : nu RI c bin i mc

Bt D4 n D7 : c gi tr ca cc bt OUT2, OUT1, DTR, RTS trong

MCR khi bt LOOP = 1.

h ) Thanh ghi trng thi ng dy . ( line status register LSR)

Thanh ghi trng thi ng dy cho bit trng thi ca vic truyn tn

hiu trn ng dy ra sao. Cc tn hiu THRE, BI, FE, PE, OE, RxDR uc th l cc nguyn nhn gy ngt nu cc Bt cho php tng ng trong

thanh ghi IER c lp

D7 D6 D5 D4 D3 D2 D1 D0

0 TSRE THRE DI FE PE OE RxDR

Bt 0 : RxDR : Receiver data ready

1 : nhn c 1 k t v n trong thanh ghi m

thu (RBR), bt ny b xo khi CPU c thanh ghi RBR

Bt 1 : OE : overrun error : li do thu )

1 : c hin tng thu (c th do CPU b chm) Bt ny b

xo khi CPU c thanh ghi LSR

Bt 2 : PE : Parity error (li parity)

1 : c li parity, bt ny b xo khi CPU c LSR

Bt 3 : FE : framing error (li khung)1 : c li khung (bt stop = 0 chng hn), bt ny b xo khi

CPU c thanh ghi LSR

Bt 4 : BI : Break interrupt (c s gin on trong khi truyn)


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Bt 5 : THRE (Transmitter holding register empty) thanh ghi gi pht

rng

1 : khi k t c chuyn t THR n TSR, bt ny b

xo khi CPU a k t ti thanh ghi THR

Bt 6 : TSRE : Transmitter shift register empty (thanh ghi dch pht rng

1 : khi mt k t c pht i bt ny b xa khi c mt

k t c chuyn t THR n TSR


21/29



Phn thc nghim


22/29



I. tng quan h thng iu khinQu trnh iu chnh tc ng c c rt nhiu phng php. vic iu

chnh bng tay hin nay vi cc dy truyn sn xut hin i hu nh khng

cn c ng dng na m thay vo l cc qu trnh n nh tc mt

cch t ng c s tr gip ca my tnh. Trong cc h thng c vic ly

tn hiu phn hi t ng c iu khin. Trong n ny mc ch chnh

l thit k hon chnh h thng n nh tc ng c in mt chiu bng

my tnh. Vic ng dng my tnh vo qu trnh iu chnh tc ng

ckhng c ngha l s vt b cc mnh in iu khin truyn thng, mmy tnh ch thay th con ngn vic iu chnh tc ng c bng tay

m thi , thng qua mt h thng t ng theo di tc ng c.

T phn tch trn ta c th dn ra mt h thng nh sau. Thng

thng iu chnh tc ng c in ta c th s dng cc phng

php nh: thay i In p t vo phn ng ng c hoc thay i t

thng... do c tnh ca my tnh l ch x l vi cc tn hiu 0,1 tc l ng

vi mc thp, mc cao ca In p. Do vy ta s chn phng php iu

chnh tc ng c In mt chiu (CTCMC) l thay i In p t

vo cun dy phn ng ca ng c (s c s iu khin phn sau) Vi

s iu khin cng vic ch yu l thay i In p (tn hiu iu khin)

vo TRANZITOR, qua khng ch in p t vo phn ng ng c, tc

ng c s c thay i ph hp. Vi h thng ang thit k cng vic

chnh l phI lm sao a c tn hiu iu khin ra mt cch t ng,

chnh xc v n nh nhanh chng tc ca ng c

Vi s phn tch trn v qua thc nghim ta c s tng quan v h

thng iu khin nh sau:


23/29



S tng quan h thng

1. Hot ng ca s :Vi h thng ny ta mong mun ng s lun n nh mt tc

t no , vic t trc tc cho ng c c thc hin bn phn mm.

Khi h thng c khi to th tc t ban u s l gi tr ca ln

thay i gn nht. Sau khi khi to ng c bt u c khi ng v

tc s tng dn n tc t v n nh tc t . Nu v mt l

do no tc ng c b thay i tc l lch khi gi tr m ta t.

Khi gi tr in p ra ca my pht tc FT s thay i. Gi tr ny tng

khi tc ng c tng ln ln hn so vi tc t ban u v ngc lI

gim khi tc ng c gim xung. Tn hiu t my pht tc ra l tin hiu

dng analog s c a vo card nghp ni v c bin i sang dng

digital ph hp vi mc tn hiu v dng tn hiu ca cng vo ni tip ca

PC. Tn hiu ni tip c a qua cng COM v chng trnh (phn mm

c vit cho qu trnh iu khin) s c c cc gi tr ny t thanh ghi

m vo ca cng ni tip, tip ch

ng trnh s x l cc tn hiu thuc v a tn hiu iu khin ph hp ra thanh ghi m pht ca cng ni

tip v c a n card ghp ni. Tin hiu c a ra ti y l tn hiu

dng Digital cha th em iu khin ng c ngay c m phi c

chuyn i sang dng tn hiu tng t analog vi bin ph hp vi mch

FT

CardNghp ni

Mchiu khin

COM

C


24/29



iu khin ca ng c, tip tn hiu s c a ti iu khin ng

c. Qu trnh c lin tc nh vy cho n khi tc ng c t c bn

gf tc t. Nhng PC th lin tc kim tra tc ca ng c k c khi

n nh.

1.Thit k giao din:

Card Ghp ni

CS

k/c

S chi tit h thng iu khin tc ng c in mt Chiu

T: Triger.

F: My pht tc.

C: ng c in mt chiu.

K/C: B khuych i tn hiu o chiu ng c.

Qua phn tch s hot ng ca h thng trn, ta thy giao din

nghp ni phI tho mn c cc nhim v sau:

B bin iNi tip-SS

A/D B bin i

Song song-nt

D/A C

Mchiu khin

T

F


25/29



1.Bin i tn hiu analog sang dng tn hiu Digital ni tip. vi mc

tn hiu ph hp vi cng RS232 (mc TTL). Sau ng khun tn

hiu trc khi a vo cng ni tip.

3.Tn hiu ra t cng ni tip c a ti Card nghp ni. Card

nghp ni c nhim v l bin i tn hiu ny sang dng tn analog

a ti iu khin tc ng c. v a ra tn hiu o chiu

ng c. T ta c s trn.

2)Chn linh kin thit k giao din.

a)Chn b bin i A/D:Trong h thng ny tn hiu t my pht tc a ti A/D ch c

mt knh. Do vy ta ch cn mt b A/D 1 knh vo, 8Bit l tho mn

yu cu. Tn hiu t my pht tc mc 0..5 (V)

Tm li ta cn phi chn b A/D c cc thng s c bn sau:

1.Tn hiu u vo analog phi tho mn t nht l 0..5 (V)

2.Tn hiu ra l tn hiu s 8 Bit (tn hiu tng thch mc TTL

l tt nht).

Ta chn dc b bin i A/D nh sau:

K hiu: ADC0804.

C cc thng s nh sau:

- Bus d liu: 8 Bit.- C li vo analog vi phn.- Tt c cc tn hiu tng thch TTL.- B pht xung nhp nm trn chip.- Gii tn hiu analog li vo 0.. .5 V. khi in p ngun nui

l 5 V.


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- Khng cn hiu chnh im khng, dng tiu th c 1,9 mAb) Chn b bin i D/A:

Iu khin mt qu trnh o c bng my tnh, cho trc mt

gi tr nn c hoc s dng my tnh nh mt b Iu khin s ta cn c

c kh nng xuta nhng gi tr analog (tng t) nh dng In nhng

gi tr analog (tng t) nh dng In v In p vi ln c th c

nh trc . t c mc ch ny thng phI ngh ngay n b bin

i D/A. T 2n gi tr s (Digital) c th b bin i D/A s to ra 2n In

p li ra khc nhau cc iin p ny c ly ra t mt In p so snh xc

nh. Ngun in p so snh c th tm thy hoc chnh bn trong b bini D/A hoc c th t mt ngun In p so snh bn ngoi. B bin i

D/A c th cho li ra lngun dng hoc ngun p

Vi h thng ca ta tn hiu Iu khin l in p iu khin qu

trnh ng m ca Tranzitor t iu chnh tc ca ng c vi vic

chn phn gii l 8 bit u vo( Digital) v u ra l ngun in p

(analog)

Cc thng s ca D/A nh sau:

- phn gii 8 bit.- u ra in p.

Ta chn c b D/A nh sau:

K hiu: AD7524

Vi u vo 8 bit tng thch mc TLL.

u ra l ngun in p 0.. .5 (V).c) Chn vi mch pht nhn khng ng b vn nng UART:

Tn hiu analog sau khi qua b bin i A/D c bin i

thnh tn hiu s (Digital) 8 bit. Vn t ra l nghp ni vo cng ni

tip tn hiu s song song cn phi c nh dng ng khun mu vi


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cng COM. V tn hiu t COM ra di dng ni tip cn phi c bin

i sang dng song song 8 bit ( ph hp vi du vo D/A). vi yu cu

nh trn ta chn c b gi ni tip sau:

- K hiu: CDP6402.Vi nhng tnh cht nh sau:

- Cng sut tiu th khng ng k :7,5 mW, Vcc=5 V.- Tc Baud: n 200 Kbaud khi in p ngun nui l +5 V.

n 400Kbaud khi in p ngun nui l +10 V.

- in p ngun nui t 4 V n 10,5 V.- Dt khun mu d liu bng phn cng.- S dng n gin.

S chn nh sau:

S b tr chn ca UART CDP 6402

VDDNCGNDRRD

D7OUTD6OUT

D5OUTD4OUTD3OUTD2OUTD1OUTD0OUT

PEFEOESFD

RRC/DRRDRRRI

123456

78910111213141516

17181920

403938373635

34333231302928272625

24232221

TRCETECRS1CRS2SBSPI

CRLD7IND6IND5IND4IND3IND2IND1IND0INTRO

TRE/TBRLTBREMR

CDP6402


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d)Cc vi mch ph:

Tn hiu ca CDP 6402 ph hp mc 0..5V. tng thch vi mc

tn hiu ca cng ni tip RS232 c mc 12...+12 V, nn phi hp gia

2 mc tn hiu ny ta dng thm vi mch MAX 232 trong mch ghp ni.

thit lp tc truyn d liu v phi hp vi PC ta s dng b

m nh phn 74HC4060. y l b m vn nng c nhng li vo ph

ni trc tip vi b cng hng thch anh do to ra c cc tn s mt

cch chnh xc v bng vic thay i v tr ca cc cu ni (Jumper) ta c

th t mt cch chnh xc cc gi tr tc Baud :2400, 4800, 9600,19200

Baud.Cc vi mch khuych i thut ton bao gm :

- 1/2LM358 lm nhim v phi hp tr khng gia tn hiu in pso snh 2,5 V vi u vo VREF ca ADC0804

- 1/2 LM358 lm nhim v tng hp tn hiu t u ra tng t caD/A AD7524.

- LM741 lm nhim v so snh gia mc tn hiu in p so snh

2,5 V v tn hiu u ca D/A c tng hp t LM358 to ra tn

hiu iu khin ng c.

- Vi mch 74HC245 lm nhim v cht s liu c ni gia u ra

ca ADC 0804 v u vo ca song song ca CPD 6402.

- Vi mch n p 7805 to ra mc in p n nh +5 V cung cpcho cc vi mch.


29/29


mc lc

A . phn l thuyt

I . o lng v ghp ni vi my tnh qua cng RS_232 4

II. Thng tin ni tip 4

1 . Thng tin ni tip vi chun RS_232 4

2. Chun ghp ni RS_232 53. B thu pht khng ng b vn nng 10

3.1. S chn 103.2. S khi 143.3. Cc thanh ghi UART 8250 16

B . phn thc nghim

II . Vi mch 26

III . Mch bin i d liu 29

IV . Phn mm

Ti liu tham kho

1 . o lng v iu khin bng my tnh Ng Din Tp

2 . K thut vi x l Vn Th Minh

3 .K thut ghp ni my vi tnh Nguyn Mnh Giang

dieu khien plc

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