an 522: as2522a/b single chip handsfree line...

AN 522:AS2522A/B Single Chip HandsfreeLine InterfaceDemo BoardApplication Note

AN522 – Preliminary Application NoteAS2522A/AS2522B

Rev. B00 Apr.01 of 25

Key features• complete handsfree telephone with AS2522 Line Interface• FSK Transmitter V.23,Bell 202, V.21, Bell103 on AS2522B only• removable 16 digit LCD module• on-chip DC-DC converter to provide power for ringing with loudspeaker; no piezo ringer required• on-board 8-bit microcontroller including 16 key matrix keypad• Jumper selectable AC impedance• easily configurable passive sidetone network on 8-pin socket• on-board opto-coupler for isolated interface to parallel PC-port for user evaluation and system design

General description This application note describes operation and features of the AS2522 Single Chip handsfree Line Interface IC including allexternal components necessary for the AN522 demoboard, which is a LCD + handsfree telephone with on-board microcon-troller.

Applications • feature handsfree telephones• All kinds of corded telephone devices with external microcontroller

PTT spec conformityThe application notes hereafter should be understood as guidelines for other designs based on the AS252x circuit. Noguarantee can be given for completeness or full conformity to PTT specification requirements. As requirements differ fromcountry to country, each required parameter must be individually tested and adjusted, if necessary.Further guidelines for adjustment is given in the documents, listed in cpt. 1: Other applicable documents and papers.



Table of contents1 OTHER APPLICABLE DOCUMENTS AND PAPERS .....................................................................................................................41.1 FURTHER APPLICATIONS ...................................................................................................................................42 REVISION STATUS ..............................................................................................................................................................................42.1 REVISION HISTORY............................................................................................................................................42.2 DEMO KIT CONTENTS ........................................................................................................................................43 GENERAL DESCRIPTION ..................................................................................................................................................................43.1 GETTING STARTED: ...........................................................................................................................................44 CONNECTOR AND JUMPER LOCATIONS .....................................................................................................................................55 CIRCUIT DESCRIPTION.....................................................................................................................................................................65.1 SWITCHING BETWEEN MODES ............................................................................................................................66 APPLICATION SCHEMATIC, ANALOGUE PART:........................................................................................................................77 APPLICATION SCHEMATIC, INTERFACE & CONTROLLER PART:......................................................................................88 AN522 DEMOBOARD: LAYOUT (TOP VIEW): ...............................................................................................................................99 AN522 DEMOBOARD: COMPONENT PRINT: ................................................................................................................................910 EXTERNAL COMPONENT SELECTION .......................................................................................................................................1010.1 PASSIVE COMPONENTS................................................................................................................................1010.2 TRANSISTORS..............................................................................................................................................1011 COUNTRY SPECIFIC SETTINGS:...................................................................................................................................................1011.1 HARDWARE AND SOFTWARE SETTINGS........................................................................................................1011.2 ADAPTION TO PAN-EUROPEAN REGULATIONS TBR21,EN301437,TBR38:.................................................1112 CONNECTING A MICROCONTROLLER ......................................................................................................................................1212.1 PORT PIN & INTERFACE DESCRIPTION..........................................................................................................1312.2 STARTUP.....................................................................................................................................................1312.3 OTHER COMPONENTS OF THE CONTROLLER PART........................................................................................1412.4 CONNECTING AN ISOLATED INTERFACE ......................................................................................................1412.5 CONNECTING THE LCD DISPLAY MODULE ..................................................................................................1412.6 SOFTWARE FEATURES OF THE ON-BOARD CONTROLLER..............................................................................1513 AS2522 BLOCK DIAGRAM ...............................................................................................................................................................1813.1 SIGNAL TRUTH TABLE: ................................................................................................................................1913.2 PROGRAMMING OPTIONS.............................................................................................................................1914 PROGRAMMING EXAMPLES: ........................................................................................................................................................2214.1 GOING OFF-HOOK ........................................................................................................................................2214.2 GENERATING A DTMF TONE.......................................................................................................................2214.3 GENERATING A SINGLE TONE FOR FSK MODULATION (AS2522B ONLY):....................................................2214.4 SETTING THE RINGING MODE .......................................................................................................................2214.5 GENERATING THE RINGER MELODY & VOLUME...........................................................................................2214.6 GENERATING A RINGER MELODY FEEDBACK IN OFF-HOOK...........................................................................2314.7 GENERATING A FLASH .................................................................................................................................2314.8 GENERATING A DIAL PULSE .........................................................................................................................2314.9 GENERATING TONES ....................................................................................................................................2314.10 MUTING THE TRANSMIT AND RECEIVE PATH ...............................................................................................2315 BILL OF MATERIALS ......................................................................................................................................................................2416 RELATED STANDARDS ....................................................................................................................................................................2516.1 APPROVALS ................................................................................................................................................2516.2 GENERAL LIABILITY DECLARATION............................................................................................................25



1 O t h e r a p p l i c a b l e d o c u m e n ts a n d pa p e r s • Data Sheet: AS2522 Single-Chip Handsfree Line Interface Circuit• Data Sheet: AS2591 16-Digit LCD Driver CMOS Integrated Circuit• Data Sheet AS2525 Single-Chip Handsfree Phone CMOS Integrated Circuit• Application Note AN525: AS2525 Single Chip Handsfree Telephone Demoboard• Application Note AN591: AS2591 LCD module• Application Notes AN500-x: General analogue telephone IC descriptions

1.1 Further ApplicationsApplications based on the AS2522 are continuously updated. Visit our home-page: http://www.amsint.com.

2 R e v i s i o n s ta t u s

AN522 Application note (this document): Rev.: B00AN522 Demoboard schematic: Rev.: A00AN522 Demoboard layout Rev.: A01

2.1 Revision HistoryRev. A00 is the first issue of this application note.Rev. B00 is an updated version which includes description of the AS2522B FSK transmitter

2.2 Demo kit contentsThe available demo-kit AN522 contains the following parts:

• AS2522 Single Chip Handsfree Phone Demoboard AN522 “ready-to-go”• AS2591 LCD module• handset• handsfree microphone• application note• AS2522 and AS2591 data sheets

3 G e n e r a l d e s c r i p t i o n

Remark: all subsequent component numbering refers to the application schematics, shown in cpt.0 .Part numbers <100 refer to the analogue part (see cpt. 0), which is basically common to all applications, part numbers>100 refer to the controller part (see cpt. 7), which will differ depending on the used microcontroller

3.1 Getting started:

• connect the handset (included in demo kit) to J2• select AC impedance (J6a, J6b)• connect the telephone line connector to J1• connect the handsfree microphone (included in demo kit) to “Mic1” , observe polarity: capsule case is negative terminal• for realistic performance check, you may connect an existing handsfree telephone with extended wires from the internal

handsfree microphone and loudspeaker• connect a 32…50Ω loudspeaker (not included in demo kit) to “LS1”• optional: connect the LCD module on J101• select line connector pins on J3,J4• operation in handset mode: activate hookswitch SW1 on left upper corner of PCB:

depressed position: on-hook, released position: off-hook• operation in handsfree mode: toggle “h/free”-switch SW2



4 C o n n e c t o r a n d J u m p e r l o c a t i o n slisted below are the various connectors and jumpers. The default settings are indicated in bold letters:

.8x

J101: connector forexternal LCD module

J102 [open]: µCreset jumper

J103: connector for isolatedremote interface

J104 [open]: power supply con-nector for isolated interface(PSTN side)

J105: power supply connectorfor isolated interface(from remote controller )

J6: test pins

J1: line connector

J2: handsetconnector

J7: VSS test pin

J3,J4 [3,4]: lineinput pin selector

J5a[closed],J5b[open]:enable/disable on-boardcurrent limiter

J6a [open],J6b[closed]: ACimpdeance setting:complex / 600Ωsee table

LS1: loudspeakerconnector

MIC1: handsfreemicrophone connector

J9 [closed]: disableoptional high startupcurrent circuit(for TBR21 only)



5 C i r c u i t d e s c r i p t i o n

5.1 switching between modesMode switching depends on external microcontroller software. With the on-board controller software, switching between modes isaccomplished in the following way:

from to Actionon-hook handset mode offhook hookswitchon-hook handsfree press h/f key (toggle function)handset mode on-hook onhook hookswitchhandset mode handsfree press h/f key (toggle function)handsfree on-hook press h/f key (toggle function)handsfree handset mode release hookswitch

Remark: loudhearing mode, although a programming option with AS2522, is not used in the sample software.

AN522 demoboard hardware mode switching:

On-Hook

Handset modeHandsfree modeoffhook: press h/f key

activate hookswitchonhook: press h/f key

onhook: release hookswitchoffhook: depress

hookswitch



6 Ap p l i c a t i o n S c h e m a t i c , a n a l o g u e pa r t :



7 Ap p l i c a t i o n S c h e m a t i c , i n t e r f a c e & c o n t r o l l e r pa r t :



8 AN 5 2 2 d e m o b o a r d : l a yo u t ( t o p v i e w ) :

0.8x

9 AN 5 2 2 D e m o b o a r d : C o m p o n e n t P r i n t :

0.8x



1 0 E x t e r n a l c o m p o n e n t s e l e c t i o n

10.1 Passive componentsAll resistors can be ¼ Watt or less, except:R9 (30Ω) P= ILine,max² * 30Ω (e.g. 0.2W @ 80mA)R30a,b (each 1k2 / 0.75W; TBR21 application only):

The maximum voltage rating for all caps is ≥6V DC, except:C1 (10µ, RI input) 25VC2 (10µ, AC impedance setting) 25VC28 (100µ, speaker decoupling) 16VC6,C7 (1µ5 ringer caps): 100VC8 (68n, DC-DC converter): 100VC29 (10µ, TBR 21 application only) 50V

10.2 TransistorsMost transistors can be general purpose types. Their function and minimum requirements are shown in the table below:

Part number Type ondemoboard

pol. function,minimum requirements

equivalent type(s)

Q1(optional) 2SA 1625K PNP hook transistor option: high voltage / high gainVCEO,VCBO: ≥-200V; hFe ≥100; IC <-100mA

KSA 1625K

Q1A,Q1B MPSA 92 PNP hook transistor option: high voltage darlingtonVCEO,VCBO: ≥-200V; IC <-100mA

MPSA 93,KSP 92/93

Q1C (optional) BSS92 P-Ch hook transistor option: VMOS,enhancement VDS ≥-200V , ID <-100mA

BSP 92 (SMD)

Q2 2N5551 NPN driver transistor for Q1VCEO,VCBO: ≥200V IC ≈ 1mA

MPSA / KSP 42/43

Q3, Q4 BC327-25 PNP line shunt regulation and Vpp supply generationgeneral purpose.: VCE <-10V , hFe ≥160 IC <-100mA, PD≤450mW

various

Q5Q6,Q104

MPSA 922N5551

PNPNPN

Q5,Q6 = DC-DC converter switchQ104: ringer startup; generate VDD from ringer signal .if not limited by ext. zener diode after bridge RB2, maximumvoltage is the peak ringing voltage. High transient voltages mayoccur during pulse dialing ( clamped by V1)

BC557 PNP opt. current limitergeneral purpose VCE <-10V

variousQ7, Q8

BC327-25 PNP opt. current limitergeneral purpose VCE <-40V , hFe ≥160 IC <-100mAPD ≤450mW

various

1 1 C o u n t r y s p e c i f i c S e t t i n g s :

11.1 Hardware and software settingsMost parameters (timings, gains, etc..) can be changed by software via the serial bus interface. See cpt. 12 for details.Some analogue parameters however, require modifications of external passive components. These are:

11.1.1 AC impedanceThe internal AC impedance of the chip is 1000Ω./real.By adding a capacitor at pin CI (#14), the synthesized impedance becomes complex (close J6b).A parallel resistor (R13A; DC-decoupled by C2) from pin LS (#13) to VSS (#9,) lowers the total AC impedance in the form of aparallel connection betweena) the IC’s impedance (1000Ω), b) R4 (typ. 10kΩ) and c) R13A: RAC = 1k //R4//R13A

Example: To set an AC impedance of 600Ω, R13A must be 1,8kΩ (close J6a and open J6b):RAC = 1000Ω // 10kΩ // 1k8 = 600Ω

Remark: When a MOSFET (optional) hook transistor is used, R4=10kΩ must be excluded from the calculation, because it is not inparallel to the line: gate-source resistance is high ohmic !)

On the demoboard, two jumpers, J6A and J6B are provided to quickly change the AC impedance between 600 Ω and complex ACimpedance. The table printed on the PCB, next to the keyboard describes the setting:

• For 600Ω, close J6A and open J6B : R13A is connected to LS and CI is left open• For complex impedance, open J6A and close J6B : no parallel resistor at LS, C3 connected to CI



11.1.2 Sidetone cancellationFor sidetone cancellation, a passive complex network (R11,R12,C5) must be connected, which should be 10 times the value of the(complex) line termination for sidetone measurements:• Sidetone network resistor values = 10 times of line termination resistor values• Sidetone network capacitor value = 1/10 of line termination capacitor value

Example: for a line termination of 270Ω + 750Ω // 150nF, the equivalent sidetone network would be(R11 + R12 // C5) = 2k7 + 7k5 // 15nF

If R13A is installed (e.g. for 600Ω impedance setting), resistor R13B (= 10 times the value of R13A) should be connected in parallelto the sidetone network to compensate for the additional load of R13AOn the demoboard, an 8-pin DIP socket is provided for the sidetone network to allow easy replacement of the components.

11.1.3 Sending and receiving frequency responseAlthough transmit and receive gains can be set by software, additional frequency shaping may be required (depending on acoustichandset characteristics). This can be done by modifying

• C17...19, R24 for handsfree sending frequency shaping• C20...22, R25 for handset sending frequency shaping• R28, C26...27 for handset receiving frequency shaping

11.2 Adaption to pan-European regulations TBR21,EN301437,TBR38:

The DB522 demoboard can be easily adapted to meet the TBR21/38/EN301437 regulations. The main change is, that a currentlimiter is required to meet the DC mask requirements for this specification.

11.2.1 Current limiterThe current limiter must be connected between hook transistor and pin LS (see schematic: optional current limiter). This device isalready installed on the demoboard, but can be bypassed with jumper J5a (J5b = open).To activate it, open J5a and close J5b.

See also cpt. 16 for links to the European Telecommunications Standards Institute.

11.2.2 Loop current after line seizureTBR21 / EN301437 requires a minimum loop current immediately after line seizure. This current will not be obtained as long as theAS2522 is in idle (=default ) mode:When the AS2522 is powered up, it is set to idle mode for minimum current consumption.The shunt line regulation is off, hence the voltage at LS (#13) will rise up to 10V, limited by the external zener diode D2.In order to bring the DC mask down, the line regulation must be activated by setting the AS2522 into one of the speech modes(command Dx).As long as the external controller can maintain to activate the speech mode(s) within 20..30ms after line seizure, the AS2522 canpass the spec without modifications.A slow controller however cannot start up fast enough to activate the speech mode in time, thus the system will fail this require-ment.For this purpose, a transistor (Q10, see options box) was installed on the demoboard, which pulls pin CS (#8) down to VSS via a5V1 zener diode immediately after off-hook. This way, the DC mask after start-up is lowered, a higher start-up current will flow andthe system can pass the TBR requirement, even when the speech modes are activated later than 30ms after line seizure.Immediately afterwards, this circuit must be disabled by the µC. In case of the demoboard, it is switched off with the HLD signal(pin#3), which is also used to hold the hook transistor in the offhook-position.Q10 can also be permanently disabled by closing J9.

11.2.3 AC impedance, Echo Return LossRqmt: The AC impedance must be set to 1000Ω / complex. Echo Return Loss must be ≥14dB @ ZREF (270Ω + 750Ω // 150nF) remove R13A and C2 (or open J6A) and remove R13B short J6B (make sure C3 is 10nF)

11.2.4 DTMF frequencies, levels & twistRequirement : DTMF level must be –9/-11 dBV, DTMF twist must be >1dB with complex line termination ZREF

Add C15 = 22pF in parallel to the ceramic resonator X1 to center the DTMF frequencies (depending on resonator) Change DTMF level to –10dB and DTMF twist to 3,2dB (adresses 02 and 03; see cpt. 13.2)

Remark: bear in mind that C3 affects both return loss and DTMF twist .Check DTMF twist with complex line termination, especiallydigit “3” (most critical, as DTMF frequencies are furthest apart). Try to make C3 as high as possible to improve Echo Return Losswhile maintaining a DTMF twist of ≥1dB.



11.2.5 DC current during ringingRqmt: In on-hook state, DC current during ringing (90Vrms, ±60VDC) must be ≤0.6mA

Make sure to use a protection element D1at tip/ring with ≥200V rating. The installed type is a DSS301L neon lamp from Mit-subishi , spark-over voltage = 255…345V

11.2.6 Sending and receiving Loudness ratingsRqmt: SLR = +3 ±4dB, RLR = -8 ±4dBWith the included handset, the loudness ratings requirements can be met by using the resistor and capacitor values shown in theapplication schematic.

Remark: if necessary, handset Tx and Rx gains can be adjusted by programming. See cpt.13.2, Addr. 0A and 0B

11.2.7 Sidetone cancellationRequirement: Sidetone cancellation is measured with 3 different terminations:a) Zref = 82Ω + 600Ω // 68nF STMR ≥ 5dBb) Zref = 270Ω + 750Ω // 150nF STMR ≥ 10dBc) Zref = 220Ω + 1800Ω // 15nF STMR ≥ 7dB

Good sidetone cancellation is achieved with the installed sidetone network: R11 = 2k7, R12 = 10kΩ,C5 = 15nF, R13B=51kΩsome fine tuning may be necessary. Generally, the sidetone network should be 10 X the line termination.R13B is to compensate resistors R4 and R32 (each 10kΩ).

1 2 C o n n e c t i n g a M i c r o c o n t r o l l e rOne of the major benefits, when using AS2522 is, that it can be interfaced with almost any microcontroller, due to the easy-to-useserial interface and the on-chip DTMF & Single tone & Ringer melody generator. This makes it no longer necessary for the control-ler to provide those signals.In the simplest form, only 3 signals are necessary to control the AS2522: Chip Select, Clock and Data In.

The DB522 demoboard uses a 20-pin / 15 port AT 89C4051 controller from ATMEL.It includes keyscan, hookswitch and ring frequency detection, serial bus and LCD module interface.



12.1 Port pin & interface description

All port pins of the µC are open-drain I/O’s, therefore some signals from the analogue part, which require high ohmic inputs cannotbe directly connected to the controller. Simple transistor circuits are used in this application to form a proper interface (see below).

The port pins are assigned as follows (I= input, O= output):

P1.0 O: Keyscan (Row1) and Chip Select for LCD module (node CS_LCD)P1.1 O: Keyscan (Row2) and Chip Select for AS2522 (node XCS)P1.2 O: Keyscan (Row3) and Chip Select for optional serial EEPROMP1.3 O: Keyscan (Row4) and Data Output for serial bus interface (node DO to send data to AS2522,

LCD module and E²PROM)P1.4 - P1.7 I: Keyscan (Columns 1..4).P3.0 I: Hook switch detection: LOW when offhook.

Q101 (simple inverter) is required to get a high ohmic input.P3.1 O: HLD; used to turn on and hold the hook transistors Q1&Q2 in offhook state via Q103 (node DPN is

pulled HIGH). DPN cannot be connected directly to the µC port pin, because it must be high ohmicin on-hook state to allow startup of Q1&Q2 when VDD is discharged.This signal is also used to turn off the optional high startup current circuit Q10

P3.2 I: FCI: Input for ring frequency and loop break detection .Q102 (simple inverter) is required to get a high ohmic input from the FCI passive network (R16,R17,C30). D101at base of Q102 is required to avoid reverse biasing of the base-emitter voltage by the ringing signal.loop breaks in off-hook state are detected as a missing signal from LI via D10 and R34 (Q102 is turned off)

P3.3 I: Handsfree button detection: LOW when handsfree button is pressedQ105 (simple inverter) is required to get a high ohmic input.

P3.4 O: Dial pulse output; LOW during flash and pulse dialing (break period): hook transistor is turned offThis signal also turns the ringer startup transistor Q104 OFF (signal NO_AC) to avoid AC current in the ringerpath during pulse dialing and flash (see also: chpt.12.3).

P3.5 O: CLK: Clock pulse for serial bus.P3.7 I: DI: DATA IN from serial bus: used to read data from AS2522 and E²PROM (DO pins)

12.2 Startup

In on-hook state, VDD is discharged, so the controller is not running. It must be woken up by either going offhook or when a ringingsignal is applied:

12.2.1 Startup in speech modeAs soon as either the hookswitch is closed or the handsfree button is pressed, The line transistor is turned on via R2,R5 and Q2.LS is clamped to 10V by the external zener diode D2 and VDD is quickly charged via LI (and an internal path from LI to VDD). Therising supply voltage generates an internal power-on-reset (POR) on both AS2522 and microcontroller.The POR sets the AS2522 into default state (see cpt. 13.2) and the microcontroller restarts.

The first job for the controller is to detect the hook event and hold the hook transistor in off-hook state by turning Q103 on. This isnecessary because in case the handsfree button was pressed, it would only turn Q2 ON, while it is closed.Therefore DPN must go HIGH, before the handsfree button is released again.The hookswitch (SW1) on the other hand, would always keep Q2 ON, as long as it is offhook (=closed).

Next, depending on hook event, the AS2522 must be set to the corresponding speech mode (handset mode, handsfree mode) bysending the proper command (“D1“ for handset mode, “D3” for handsfree mode) to the serial bus.

The AS2522 serial interface will accept commands, as soon as VDD is powered up. See cpt. 0 for further AS2522 programmingexamples.



12.2.2 Startup in ringing modeIn ringing mode, the controller must be woken up by the AC ringing signal, as no DC current is available. Therefore, a startup cir-cuit, basically a simple voltage regulator (Q9) is provided to generate a supply for the startup phase in ringing mode. See pro-gramming examples in cpt. 0 for further reference.

Once the DC-DC converter is running, power for the speaker supply (VPP) is generated. This voltage will also charge VDD (viaD7) and aid the startup circuit.

12.3 Other components of the controller partD103 is used to turn off the startup circuit (Q9) during flash or pulse dialing breaks. This avoids unwanted current to be drawn fromthe line caused by the high transients at VRING, when the hook transistor is turned off.

An optional E²PROM may be connected at the serial bus. It is used to store user defined settings. See cpt.12.6.2 formore detailed descriptions.A relatively low ceramic resonator frequency of about 680kHz was chosen for low power dissipation.

12.4 Connecting an isolated InterfaceFor customer design and evaluation apart from the on-board microcontroller, an isolated interface is provided to generate serialbus commands for the AS2522 by an external data source. The optical isolation enables usage of earthed controlling devices, suchas PC ports, etc.The on-board connector is 1:1 compatible with the parallel LPT port of the PC.

An external power (VCC) is required to drive the LED’s of the opto-couplers. With the installed series resistors (R111...113), VCCmust be about 5V.The AS2522 serial bus interface requires fast rise/fall times, therefore opto-couplers with schmitt-trigger inputs and low ohmic pull-up resistors must be used.

The external power supply can be connected at J105.

In order to generate VCC from the LPT interface of a PC, D105..107 can be installed to generate about 5V from the AUTOFEED,INIT and SELECT signals of the parallel port interface. However, these port outputs cannot drive large currents. Therefore thesoftware, controlling the interface, must make sure that the LPT data outputs D0..D2 are HIGH in default state, so the LED’s don’tdraw current.

To avoid bus conflicts between the opto-coupler interface and the on-board microcontroller, the controller must be disabled, whenserial bus commands are sent by the isolated interface. This can be done by closing jumper J102 (pull the RESET pin of the con-troller HIGH, all Port pins = open collector outputs are high ohmic). You can also disable the controller by software, see cpt.12.6.3for further reference.

On the other hand, when the controller is sending data, the opto-couplers must be high ohmic. This can be accomplished, wheneither all outputs D0..D3 are HIGH (LED’s = off), or the Sub-D connector J03 is disconnected.Diodes D108..110 prevent collision, when the opto-coupler output is HIGH and the controller drives a LOW at the bus.

The output drivers of the H11L1 opto-couplers draw relatively large current (total ≈3..5mA) from VDD.This may cause problems with discharging of VDD at small line currents or long flashes. Therefore it is recommended to supplythe opto-couplers with external power: open J104 and connect an external voltage of about 4..6V at pin “ext” of J104.

Caution: the external supply must be isolated from Earth, when the demoboard is connected to a PSTN line !

12.5 Connecting the LCD display module

The AS2591 based LCD display module is described in the AN591 Application Note.



12.6 Software features of the on-board controllerThe following flowchart describes the basic features of the on-board controller software:Tone/Pulse Dialing, Flash, Volume control and programming:When going off-hook, the software responds by displaying the actual revision number (e.g. “Pro 2-00”).If the (optional) E²PROM is not installed, “no Epr” is also displayed.

12.6.1 Sending serial bus commands to the AS2522The PROG key can be used to send commands to the AS2522 in the form of a 2-digit (8bit) HEXcode. This mode is invoked by pressing “P” (PROG) and then entering the 2 digit Hex code.Since there is only a 16-digit keypad installed, the HEX-codes must be entered, using the addi-tional keys as shown on the right:After the code is entered, it must be terminated by pressing “P” again in order to send that codeto the AS2522.If a key other than “P” is entered as the 3rd key entry, the code will not be sent and the programreturns to speech mode (see flowchart).

1 2 3 C

4 5 6 D

7 8 9 E

A 0 B F

speech mode (handset / handsfree)

key0...9,*,#pressed

digit is dialed out(default = DTMF)

Flash key(R)

pressed

flash is ececuted(default = 100ms)

Programkey (P)pressed

Receive volume is changed:

h/s-mode: earpieceh/f-mode: speaker

Volume key(VOL+/-)pressed

Enter 2-digit HEX

code*)

2 digit HEX codeis sent toAS2522

Programming mode

key "P"pressed ?

Yes

no

*) Hex code must be 10...FF Code 00...0F = special functions

AN522 demoboard controller software:



12.6.2 E²PROM memory mappingIf an E²PROM is installed, some settings will be stored and reloaded at next off-hook (see below).The values are stored as a 1-byte variable according to the AS2522 command list in cpt.13.2.The parameters are being stored at next on-hook:

Addr. block [Hex] Function Values

00 E²PROM-check byte AA

02 Flash time ( value*10 ms, e.g.64H = 100 ms) 6406-26 32 digits last number redial32 DTMF level 2 x33 DTMF:confidence tone & level, Preemphasis 3 x36 Ring amp.ON,Noise monitoring and soft clipping 6 x38 Handsfree receive end gain; speaker volume 8 x39 Handsfree voice switching speed 1/2/4/8x 9 x3A Transmit gain A x3B Receive gain B x3C DC-mask, Line Loss Compensation C x41-61 Pre-dialer number (32 digits)

To return to the default settings, the E²PROM must be erased (see cpt.12.6.3, code 06).

12.6.3 Special functionsThe onboard software provides some additional features, which can be invoked by hex-codes 00...0F:

Code 00: Reading the LLC status information:

Syntax: P 00 P

In this mode, the controller repeats polling the LLC status from the AS2522 by sending the NOP (00) command andreading the DO pin of the AS2522. The status is displayed in the form “LLC 000” ....”LLC 006”, respective to the readingas shown in cpt. 13.2, Command 0x.This mode can be terminated by pressing the “0” key, after which the software will return to programming mode

Code 01: Setting the Flash time:

Syntax: P 01 Code

In this mode a 2-digit decimal number can be entered to program the approximate flash time in the form of:[ ]

Codeflashtime ms

≈10

e.g. for 200ms flash time, enter “20”

If an E²Prom is installed, the new setting will be stored and remains the active flash time as long as it is not changedagain.If no E²Prom is installed, the changed setting will remain the active flash time until on-hook. The default flash time afteroff-hook is 100 ms.After the 2 digits are entered, the software will return to programming mode.

Remark: depending on external load on VDD (e.g. when the isolated opto-coupler interface is installed and supplied with-out external power) long flashes will result in discharge of VDD.

Code 02: Toggle DTMF / Pulse dialing mode:

Syntax P 02 P

This code toggles between DTMF and pulse mode. The pulse m/b ratio is 60/40 and the dialing mode is not stored in theE²PROM. The default dialing mode is always DTMF after off hook. The active dialing mode can be realized by the re-spective symbol (tone / squarewave) on the LCD display.



Code 03: Disable the microcontroller for isolated interface operation (handsfree mode only):

Syntax P 03 P

When invoking this command, the controller will set all output ports to HIGH (open collector) and disable the keyscan.This allows the optional isolated interface to send and receive data to/from the AS2522 without being disturbed by themicrocontroller. The mode is indicated by displaying “P” on the LCD display.

To resume to programming mode, the handsfree key must be pressed shortly.

Code 04: Last number redial (only available, when E²Prom is installed):

Syntax P 04 P

After entering this sequence, the last manually entered digits are re-dialed. The maximum number of digits is 32.After redialing, the software returns to speech mode.

Code 05: Pre-dialer for provider access

Syntax P 05 P

This command saves the contents of the last manually entered number (contents of LNR) as the provider access code.Digit * is converted to a 1 second pause.

Example: 0-Pause-1002 shall be dialed prior to any manually entered number after off-hook:offhook – dial 0*1002 – P 05 P

This feature can be ignored by pressing # as the first digit after off-hook. Dialing will continue with the number(s) enteredafter #.To clear the pre-dialer, enter: P 05 P immediately after off-hook.

Code 06: Erase Data in E²PROM

Syntax P 06 P

This command will erase all data in the external E²Prom. However, even a blank E²PROM will be detected by the con-troller software and prepared for further use with the system.Therefore, an E²PROM with unknown contents shall be erased first.

Code 07...0F:

currently not used



1 3 AS 2 5 2 2 B l o c k D i a g r a m



13.1 Signal truth table:

CS

CLK

↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓DI (from µC) A3 A2 A1 A0 D3 D2 D1 D0

DO (frm. AS2522) LLC5 LLC4 LLC3 LLC2 LLC1 LLC0 S1 S0

For programming the AS2522, three signals are required: Chip Select (XCS), Clock (CLK), and Data In (DI).The 4th signal, Data Out (DO) is only used for reading the LLC and power-on-reset (POR) status. It is not required for mode pro-gramming. While CS is high, DO is high-Z.

The falling edge of CS enables the internal shift register. Data at DI is read with every rising edge of CLK, A3 must be clocked infirst, D0 is last. After 8 clock pulses, CS should be pulled high. With the rising edge of CS, the shift register data is sent to theinternal registers.

Simultaneously with every falling edge of CLK, the LLC and POR status information is sent out at DO. The first 6 bits are the LLCstatus bits with the MSB sent first, followed by the two POR status bits. if more than 8 clock pulses are sent, DO will output “0”-s.For reading the status information without changing the state of the AS2522, it is recommended to send a NOP (0x) command, seebelow:

13.2 Programming optionsEach command consists of a 4-bit address and 4 bit data. The following commands are possible:

Command[Hex]

A3 A2 A1 A0 D3 D2 D1 D0 default settings are shown in D3...D0 and in bold letters:

No Operation, this command does not change the current statusof the chip, it may be used to read the LLC and POR status atthe DO pin (see signal truth table)LLC status has 7 states, indicating the attenuation of Tx/Rxgains with increasing line current (approx. value)Remark: LLC=OFF will always read 000000SS

LLC = LO<20mA

20-26mA26-32mA32-38mA38-44mA44-50mA>50mA

LLC=HI<45mA

45-51mA51-57mA57-63mA63-69mA69-75mA>75mA

reading at DO000000SS000001SS000011SS000111SS001111SS011111SS111111SS

Tx/Rx rel.gain0

-1dB-2dB-3dB-4dB-5dB-6dB

0x 0 0 0 0 x x x x

POR status (bits S1/S0):CS= Low, S1/S0 =10: ready to receive data:CS= Low, S1/S0 =all other combinations: not ready

DTMF frequency Single Tone Frequencies

10...1F 0 0 0 1

C1

0000000011111111

C0

0000111100001111

R1

0011001100110011

R0

0101010101010101

Data[Hex]

0123456789ABCDEF

DTMF-Tone

147*2580369#ABCD

Fre-quency.

0Hz800Hz

1067Hz1333Hz1300Hz2100Hz1200Hz2200Hz980Hz

1180Hz1070Hz1270Hz1650Hz1850Hz2025Hz2225Hz

AS2522B onlyFSK=1 (Addr. C)

Ring-melody.Ring-melody.Ring-melody.V.23V.23Bell 202Bell 202V.21V.21Bell 103Bell 103V.21V.21Bell 103Bell 103



DTMF level (low group @ LS)

20...2C 0 0 1 0

0000000011111

0000111100001

0011001100110

0101010101010

0123456789ABC

-16dBm-15dBm-14dBm-13dBm-12dBm-11dBm-10dBm-9dBm-8dBm-7dBm-6dBm-5dBm-4dBm

30...3F 0 0 1 1 T0

P1

C20

C11

DTMF: confidence tone & level, PreemphasisT = TONE = DTMF path on[1]/off[0]P = DTMF twist: 2,2dB[0]/ 3.2dB[1]C2/C1: confidence tone level @RO /LO1,2 rel. to LS:00 = -36dB -15dB01 = -30dB -9dB10 = -24dB -3dB11 = -18dB +3dB

40...4F 0 1 0 0 F10

F00

V10

V00

Ringer melody: frequency & Volume (PDM), beep freq.F1,F0: 00 = 800Hz, 01=1067Hz, 10=11=1333HzV1,V0: 00=-17.5dB, 01=-11.5dB, 10=-5.5dB, 11=0dB

ABR

ABS

T1 T0

50...5F 0 1 0 1

0 0 0 0

DTMF/Single Tone analogue generator:ABR: Tone is sent to receiver (RO) : on[1] / off[0]ABS: Tone is sent to Speaker (LO1/2) : on[1] / off[0]

T1/T0: (frequency may be changed with addr.4)00 = Tone generator OFF01 = DTMF ON (send to line, Ro and/or LO1/2)10 = Single tone ON (sinewave @ line,RO,LO1/2)11 = Ringer tone ON (digital PDM signal @ LO1/2 only)

60...6F 0 1 1 0 R0

B0

SR0

ST0

Ringer amp. ON, Noise monitoring and soft clipping:R: Ringer amplifier LO1/2: on[1] / off[0]B: handsfree background noise monitoring: on[1] / off[0]SR: Soft clipping at RO: on[1] / off[0]ST: Soft clipping at LS: on[1] / off[0]

DBr

DBs M D

70...7F 0 1 1 1

0 0 0 0

power-down: beep, MASK and DC-DC converter:DBR: digital signal@ RO (for beep in power down) [0]DBL: digital signal @LO1/2 (for beep in power down)[0]M: MASK:[0]: normal, [1]: power save; LI forced to 0.7V(for LD dialing)D: DC/DC-converter on[1] / off[0]

80...8F 1 0 0 0 X0

x1

x1

x1

Handsfree receive end gain; speaker volume [0111]16 steps, total attenuation range = -20dB:0000=min Vol; Rx gain = -20dB; Tx gain = -30dB1111=max Vol; Rx gain = 0dB; Tx gain = -50dB



Handsfree voice switching speed 1/2/4/8x:S1,S0: 00 ≈ 1ms / 6dB (maximum speed ) 01 ≈ 2ms / 6dB 10 ≈ 4ms / 6dB 11 ≈ 8ms / 6dB (minimum speed)with BNM on, switching from Tx->idle, Rx->idle is≈30/60/120/240 ms/6dB respectivelyO0,O1 Background Noise Monitor Offset

90...93 1 0 0 1 O11

O00

S10

S00

O10011

O00101

BGN-offset120mV180mV240mV300mV

Transmit gain [0111]

A0...AF 1 0 1 0

T3

0000000011111111

T2

0000111100001111

T1

0011001100110011

T0

0101010101010101

Data[Hex]0123456789ABCDEF

Handset mode30 dB31 dB32 dB33 dB34 dB35 dB36 dB37 dB38 dB39 dB40 dB41 dB42 dB43 dB44 dB45 dB

Handsfree mode39 dB40 dB41 dB42 dB43 dB44 dB45 dB46 dB47 dB48 dB49 dB50 dB51 dB52 dB53 dB54 dB

Receive gain [0111]

B0...BF 1 0 1 1

R3

0000000011111111

R2

0000111100001111

R1

0011001100110011

R0

0101010101010101

Data[Hex]

0123456789ABCDEF

handset mode:LS->RO-6 dB-5 dB-4 dB-3 dB-2 dB-1 dB0 dB1 dB2 dB3 dB4 dB5 dB6 dB7 dB8 dB9 dB

handsfree mode:LS->LO1/2@max vol.22 dB23 dB24 dB25 dB26 dB27 dB28 dB29 dB30 dB31 dB32 dB33 dB34 dB35 dB36 dB37 dB

C0...C7 1 1 0 0 FSK

0L1

A11

A01

FSK-mode,DC-mask, Line Loss Compensation:L= LI-Voltage: [0]= 3,5V, [1]= 4,5VA1,A0: 11= 01 = noLLC, 00= LO (20-50mA), 10= HI (45-75mA)reading LLC status : see Addr 0 descriptionFSK: frequency select in single tone mode AS2522B onlyFSK=0 Single tone frequ. are read from Addr.4: F1,F0FSK=1 Single tone frequ. are read from Addr.1: C1,C0,R1 RO

D0...DF 1 1 0 1 S30

S20

S10

S00

Speech modes: S3,S2,S1,S0:0000 = power down, no line regulation0001 = Handset mode0011 = Handsfree mode0101 = Loudhearing mode (no anti-larsen)1xx1 = Transmit path is muted

E0...EF 1 1 1 0 x x x x for factory testing only [0000]Fx 1 1 1 1 x x x x Reset to default settings



1 4 P r o g r a m m i n g e x a m p l e s :The following examples give some guidelines on how to perform specific functions when using the AS2522 in a system design. Allcommands, addresses and data are in Hex-numbers, component numbers refer to the AN522 schematic in cpt. 0:

14.1 going off-hookAfter power up (close hookswitch & apply line current), the AS2522 line regulation is inactive (see Addr. D). The shunt transistor,controlled by pin CS is off and LS is clamped to 10V by the external zener diode.The first command must therefore turn on the AS2522 in the desired speech mode :command = D1 for handset mode, D3 for handsfree mode.Afterwards, if necessary, the other parameters, like DC-mask, Line loss compensation, Tx-Rx gains and soft clipping can be sent.For handsfree operation, voice switching speed, speaker volume and background noise monitoring can be selected.

14.2 generating a DTMF toneDTMF tones can be sent in any of the speech modes. Prior to turn the DTMF generator on, a few parameters, like DTMF fre-quency, level and preemphasis must be set. Confidence tone (DTMF signals in the earpiece) level can be selected.An analogue path must be switched to feed the DTMF signal onto the line:DTMF level (command = 20...2C) must be set at least once, e.g. after startup.

14.2.1 sending a DTMF tone:a) activate DTMF generator in addr. 5: e.g. command = 51 (DTMF generator ON)b) select DTMF frequency: in addr.1: e.g. command = 10 (select DTMF signal “0”)c) activate Tone-bit in addr. 3 and select preemphasis & confidence tone level: e.g. command = 3F (DTMF path active, Twist = 2.6dB, confidence tone = +3dB)

14.2.2 turning the DTMF signal off and returning to speech mode:a) turn DTMF generator off in addr. 5 : e.g. command = 50 (DTMF generator OFF, confidence tone paths disconnected)b) return to speech path in addr 3 : e.g. command = 37 (analogue path active, Twist and confidence tone are not mandatory

now)

14.3 generating a single tone for FSK modulation (AS2522B only):FSK tones can be sent in any of the speech modes. Prior to turn the single tone generator on, a few parameters, like FSK fre-quency and level must be set. Confidence tone (FSK signal in the earpiece) level can also be selected.An analogue path must be switched to feed the FSK signal onto the line:FSK level (command = 20...2C) must be set at least once, e.g. after startup.

14.3.1 Sending a FSK tone:a) select single tone register for FSK modulation in addr. C: e.g command = C8 (single tone frequencies are read from Addr.4)a) activate single tone generator in addr. 5: e.g. command = 52 (Single tone generator ON)b) select single tone frequency in addr.1: e.g. command = 14 (select FSK tone for V.23 1300Hz)c) activate Tone-bit (addr.3) & select confidence tone level: e.g. command = 3B (FSK path active, confidence tone = +3dB)

14.3.2 turning the FSK signal off and returning to speech mode:see cpt. 14.2.2

14.4 setting the ringing modeIn ringing mode, the hook transistor is always off, and there is no DC line current available to supply the AS2522 or external µC.The AS2522 must be in power down mode (default after startup, command = D0) .During the complete ringing phase, the circuit must be supplied by the AC ringing signal. For fast wakeup, a startup circuit must beimplemented (Q104) , to quickly supply VDD for the µC.The DC-DC converter should be turned on next, to generate VDD and VPP (speaker supply).command = 71 (turn DC-DC converter on)If ring frequency detection (Q10) is supported, the ring frequency must be checked for a valid ringing signal, before a ringer melodyis output. During the complete ringing circle, the hook switch(es) must also be monitored.

14.5 generating the ringer melody & volumeFor maximum output power, the ringer melody is output as a digital signal at RO1, while RO2 is forced to VSS. The AS2522 pro-vides an on-chip single-tone ringer melody generator with digital pulse-density modulated (PDM) volume control. There are 3 mel-ody frequencies and 4 volume settings available.The actual ringer melody sequence, which repeats 2 or 3 frequencies at a certain rate, must be provided by the controller.Example: generating a sequence of 800Hz + 1067Hz + 1333Hz: at maximum volumea) turn ringer generator on in addr. 5: e.g. command = 53 (ringer generator ON)b) select frequency & volume in addr. 4: e.g. command = 43 (f=800Hz, vol = max)

c) turn ringer amplifier on in addr 6:



e.g. command = 68 (Ringer amp ON) Rem.: VPP supply is required, usually from DC-DC converterd) after some delay (wait cycle from controller), change the melody frequency, as in pt a):

e.g. command = 47 (f=1067Hz, vol = max)e) repeat step d with another frequencyf) after completion of ringing, you may turn the ringer generator and amplifier off:

e.g. command = 50 (generator OFF)e.g. command = 60 (amplifier OFF)

14.6 generating a ringer melody feedback in off-hookThe sequence, described in cpt. 14.5 also works in off-hook state, so it may also be used for acoustic feedback during ringer mel-ody programming.

14.7 generating a flashA flash is a timed interruption of the line, consequently it must be performed by turning off the hook transistor during the flash (Q6,via Q7). However, as soon ad the hook transistor is turned off, there is no more line current available to support the ICs. Therefore,VDD must be supplied from the buffer capacitor (C10). To avoid fast discharge of the VDD buffer cap by high supply current duringthe flash, the AS2522 shall be switched to a power-save mode:command = 72 (MASK-bit = 1).

14.8 generating a dial pulseThe break-period of a dial pulse is generated in the same way as a flash (see cpt.14.7), the make-period is generated by turningthe hook transistor on while leaving the AS2522 in the power-save mode (MASK-bit = 1). In power-save, LI is pulled down to 1.2V,resulting in a low DC-resistance at the tip/ring terminals during the make-period.

14.9 generating tonesThere are four types of acoustic feedback signals available:• a DTMF signal, which can be sent to the line, the earpiece and the speaker (see cpt. 14.2)• a FSK signal, which can be sent to the line, the earpiece and the speaker (AS2522B only)• a single tone analogue signal, which can be sent to earpiece and speaker, e.g. for alert signals in speech mode• a single tone digital signal, which can be sent only to the speaker, either as a strong (ringing) signal or as weak (beep) signal

14.9.1 generating a DTMF tonesee cpt. 14.2

14.9.2 generating a single tone for FSK modulation (AS2522B only):see cpt. 14.3

14.9.3 generating a single tone during speech modeYou can generate a single, sinewave tone in the earpiece or speaker during active speech mode (e.g. as an alert signal), by turningthe ABR and ABL switches ON (see block diagram). This tone is not sent to the line, as long as the TONE – bit (0011 X...) is notset.

e.g. command = 5A (single tone at earpiece ) Remark: will also be audible in the speaker in handsfree mode, when voice switch-ing is switched to Rx modee.g. command = 56 (single tone at speaker ) Remark: handsfree mode must be active, tone only in speaker, independent of voiceswitching

14.9.4 generating a digital tone in speakerThe generation of a ringer melody is described in cpt. 14.5. You may generate a short beep at the speaker and/or earpiece as anacoustic feedback for various purposes, e.g. acknowledgement of a keypress.This beep can also be generated in power-down mode (for example, when a key is pressed, while the chip is in power-save modeduring pulse dialing), as long as the beep is short enough to avoid excessive discharge of the VDD buffer cap.For this purpose, weak buffers with small current driving capability for RO and LO1 are supported on-chip. To activate these driv-ers, you may turn on the DBR (receiver) and/or DBL (speaker) bit in addr 7:e.g. command = 43 (f=800Hz,vol= max) Rem.: the beep frequencies and levels are the same as for the ringer signale.g. command = 53 (digital generator ON)e.g. command = 74 (beep at speaker)e.g. command = 78 (beep at earpiece)

14.10 Muting the transmit and receive pathThe transmit path can be muted by setting bit S3 of addr. D.:command = D9 (for handset mode), command = DB (for handsfree mode)There is no dedicated mute-bit for the receive path, but you may mute the receive path by switching to DTMF mode while the tonegenerator is off: command = 50 (Tone generator = off).command = 38 (TONE = ON, receiver path disconnected from RO amplifier).



1 5 B i l l o f m a t e r i a l sThe following table shows the component count of the complete application to allow quick calculation of the BOM.As prices depend on quantity, vendor, etc. they must be filled in individually:

Analogue part: type of component #of components Unit price sumIC: AS2522 1Resistor, ¼ Watt 29Capacitor , ceramic, <50V 12Capacitor, ceramic, 100V 1Capacitor, film, 100V 2Capacitor, pol. <=100µF / <16V, 11Capacitor, pol. >=220µF / <=6V 3Diode, general purpose 1Diode, >200V 3Diode, Zener, 0.5W 3Diode, Zener, 1W 1Inductor, ≈2,2mH ≤20Ω 1Transistor, general purpose 2Transistor, low power high voltage 4Overvoltage suppressor 1Ceramic resonator, 3.58MHz 1Rectifier bridge, 200V 2Handsfree electret microphone 1Speaker, 32...50Ω 1

Controller part: type of component #of components Unit price sumIC: microcontroller 1IC: EEPROM (opt). 1Resistor, ¼ Watt 10Transistor, general purpose 5Ceramic resonator 1Capacitor , ceramic, <50V 2Reset button (opt). 1

LCD module:type of component #of components Unit price sumIC: AS2591 1IC: 3V voltage regulator (opt). 1Resistor, ¼ Watt (opt) 2Resonator 32,768kHz 1Capacitor , ceramic, <50V 3Diode, Schottky (opt) 1Capacitor, pol. >=220µF / <=6V 1LCD display: 12 or 16 digits 1

Option: Current limiter: #of components Unit price SumResistor, ¼ Watt 2Resistor, 1.5 Watt (or 0.75W) 1 (2)Transistor, general purpose 2Capacitor, pol. 10µ/50V 1

Option: Isolated Interface: #of components Unit price Sumlow current opto-coupler 3 (4)Resistor, ¼ Watt 3 (5)Transistor, general purpose (1)

Other components (individual) #of components Unit price SumHandset 1PCBKeyboardTOTAL



1 6 R e l a t e d Sta n d a r d s

The product, AS25xx, is designed to be in compliance with ETSI standards for connection to the analogue PSTN of terminalequipment including voice telephony services or other voice band communication when installed into a properly designed system.The specification of the product is based on following standards and requirements:

NET 4 ETS 300 001, PSTN basic access; analogue terminal equipmentgeneral requirements, March 1996.

EN55022 EMC ( Electro Magnetic Compatibility)IEC 1000-4-3 Electromagnetic Irradiation (CE approval)TBR 21 pan-European approval for connection to the analogue Public Switched Telephone Network (line inter-

face part)TBR 38 pan-European approval for connection to the analogue Public Switched Telephone Network (acoustics).

See http://www.etsi.org for further information

Note: Some national PTT authorities may have additional requirements exceeding the above standards and requirements.Such additional requirements have only been respected to the extent that they were known to Austria Mikro Systemeprior to designing the product. However, Austria Mikro Systeme shall not be liable to recipient or any third party in con-nection with the approval procedures of applications in which the AS25xx is used.

16.1 Approvals

Since the AS25xx is a component and not a complete system, it can not be approved as a stand alone part by the standards bod-ies. Hence, full conformance to above standards is depending on the application in which the AS25xx is being used, and therefore,approvals by the standards bodies are the responsibility of the customer and Austria Mikro Systeme will not have tested the prod-uct to meet the above standards.

16.2 General Liability DeclarationCopyright 1999, Austria Mikro Systeme International AG, Schloß Premstätten, 8141 Unterpremstätten, Austria.Telefon +43-(0)3136-500-0, Telefax +43-(0)3136-52501, E-Mail [email protected] rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by anymeans, without the prior permission in writing by the copyright holder. To the best of its knowledge, Austria Mikro Systeme Interna-tional asserts that the information contained in this publication is accurate and correct.

an 522: as2522a/b single chip handsfree line...

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