MITEL MT9126AE, MT9126AS Datasheet



CMOS

MT9126

Quad ADPCM Transcoder

Preliminary Information

Features

• Full duplex transc ode r with four e ncod e channels a nd fou r de code c hanne ls

• 32 kb/s, 24 kb/s and 16 kb/s ADPCM coding complying with ITU-T (previously CCITT) G.726 (without 40 kb/s), and ANSI T1.303-1989

• Low power o perat ion, 25 m W ty pical

• Asynchronous 4.096 M Hz m aster clock operation

• SSI and ST-BUS interface options

• Transparent PCM b ypass

• Transparent ADP CM bypa ss

• Linear PCM cod e

• No microprocessor control requi red

• Simple inter face t o Code c devi ces

• Pin select a ble µ−Law or A-Law o perat ion

• Pin selectable ITU-T or signed magnitude PCM coding

• Single 5 vol t pow er suppl y

Applications

• Pair gain

• Voice mail systems

• Wireless telephony systems

ISSUE 2 May 1995

Ordering Information

MT9126AE 28 Pin Plastic D IP MT9126AS 28 Pin SOIC

-40 °C to +85 °C

Description

The Quad ADPCM Transcoder is a low power, CMOS device capable of four encode and four decode functions per frame. Four 64 kbit/s PCM octets are co mpressed into fou r 32, 2 4 or 16 kbit/s ADPCM words, and four 32, 24 or 16 kbit/s ADPCM words are expanded into four 64 kbit/s PCM octets. The 32, 24 and 16 kbit/s ADPCM transcoding algorithms utilized conform to ITU-T Recommendation G.726 (excluding 40 kbit/s), and ANSI T1.303 - 1 989 .

Switching, on-the-fly, between 32 kbit/s and 24 kbit/s ADPCM, is possible by controlling the appropriate mode select (MS1 - MS6) control pins. All optional functions of the device are pin selectable allowing a simple interface to industry standard codecs, digital phone devices and Layer 1 transceivers. Linear coded PCM is provided to facilitate external DSP functions .

ADPCMi

ADPCMo

ENB1

ENB2/F0od

BCLK

F0i

MCLK

C2o EN1 EN2

Timing

VDD VSS PWRDN

Full Duplex

ADPCM

I/O

Quad

PCM

I/O

Transcoder

Control Decod e

IC MS1 MS2

FORMAT MS5MS4MS3 MS6 LINEAR SEL

A/µ

Figure 1 - Functional Block Diagram

PCMo1 PCMi1

PCMo2 PCMi2

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MT9126 Preliminary Information

EN1

MCLK

F0i

C2o

BCLK

PCMo1

PCMi1

VSS

LINEAR

ENB2/F0od

ENB1

PCMo2

PCMi2

SEL

1 2

3 4 5

6 7 8

9 10 11 12 13 14

28 27 26 25 24 23 22 21 20 19 18 17 16 15

EN2 MS6 MS5 MS4 ADPCMo ADPCMi VDD MS3 MS2 MS1 IC PWRDN FORMAT A/µ

Figure 2 - Pin Connections

Pin Description

Pin # Name Description

1 EN1 Enable Strobe 1 (Output). This 8 bit wide, active high strobe is active during the B1

PCM channel in ST-BUS mode. Becomes a single bit, high true pulse when LINEA R=1. In SSI mode this output is high impedance.

2 MCLK Master Clock (in pu t). This is a 4.096 MHz (minim um ) input clock utilized by the

transcoder function; it must be supplied in both ST-B US and SSI modes of operation. In ST-BUS mode the C4

ST-BUS clock is applied to this pin. This synchronous clock is

also used to control the data I/O flow on the PCM and ADP CM input/out put pins according to ST-BUS requirements.

In SSI mode this master clock input is derived from an external sour ce and may be asynchronous with respect to the 8 kHz frame. MCLK rates greater than 4.096 MHz are acceptable in this mode since the data I/O rate is governed by BCLK.

3F0i

4 C2o 2.048 MHz Clock (Ou tput). This ST-BU S mode bit clock output is the MCLK (C4

Frame Pulse (Input). Frame synchronization pulse input for ST-BUS operation. SSI

operation is enabled by connecting this pin to V

) input

divided by two, inverted, and synchronized to F0i

. This output is high-impedance during

SSI operation.

5 BC LK Bit Clock (In put). 128 kHz to 4096 kHz bit clock input for both PCM and ADPCM p orts;

used in SSI mode only. The falling edge of this clock latches data into ADPCMi, PCM i1 and PCMi2. The rising edge clocks data out on ADPCMo, PCMo1 and PCMo2. This input must be tied to V

for ST-BUS operation.

6 PCMo1 Serial P CM Stream 1 (Outpu t). 128 kbit /s to 4096 kbit/s seri al companded/ linear PCM

output stream. Data are clocked out by rising edge of BCLK in SSI mode. Clocked out by MCLK divided by two in ST-B US mode. See Figure 1 4.

7 PCMi1 Serial PCM Stream 1 (Input). 128 kbit/s to 4096 kbit/s serial companded/line ar PCM

input stream. Data are clocked in on falling edge of BCLK in SSI mode. Clocked in at the 3/4 bit position of MCLK in ST-B US m ode. See Figure 14.

Digital Groun d. Nomi nally 0 volts.

9 LINEAR Linear PCM Selec t (Inpu t ). When tied to V

bit linear PCM. Linear PCM operates only at a bit rate of 2048 kbit/s. Companded PCM is selected when this pin is tied to V

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the PCM I/O ports (PCM 1, PCM 2) are 16-

. See Figures 5 & 8.

Preliminary Information MT9126

Pin Description

Pin # Name Description

10 ENB2/F0od PCM B-Chann el Enab le Strob e 2 (Input) / Dela yed Fr ame Pu lse (Outpu t).

SSI operation: ENB2 (Input). An 8-bit wide enable strobe input defining B2 channel (AD)PCM data. A valid 8-bit strobe must be present at this input for SSI opera tion. See Figures 4 & 6.

ST-BUS operation: F0od EAR=0, this becomes a delayed frame pulse outp ut occurring 64 C4

and when LINEAR = 1 at 128 C4 clock cycles after F0i . See Figures 7, 8, 9 & 14.

F0i

(Output). This pin is a delayed frame strobe output. When LIN-

clock cycles after

11 EN B1 PCM B-Channel Enab le Strobe 1 (Inp ut).

SSI operation: An 8-bit wide enable strobe input defining B1 channel (AD)PCM dat a. A valid 8-bit strobe must be present at this input for SSI operation.

ST-BUS operation: When tied to V nels is enabled. When tied to V

transparent bypass of the ST-BUS D- and C- chan-

the ST-BUS D-channel and C-channel output timeslots

are forced to a high-impedance state.

12 PCMo2 Serial P CM Stream 2 (Outpu t). 128 kbit/s to 4096 kbit/s serial co mpanded/line ar PCM

output stream. Clocked out by rising edge of BCLK in SSI mode . Clocked out by MCLK divided by two in ST-BUS m ode. See Figure 14.

13 PCMi2 Serial PCM Stream 2 (Input). 128 kbit/s to 4096 kbit/s serial companded/linear PCM input

stream. Data bit s are clocked in on falling edge of BCLK in SS I mode. Clo cked in at the 3/4 bit position of MCLK in ST-B US m ode. See Figure 14.

14 SEL SELECT (Input ).

PCM bypass mode: Wh en SE L=0 the PCM 1 port is selected for PC M bypass operation and when SEL=1 the PCM2 port is selected for PCM bypass operati on. See Figures 6 & 9.

16 kbit/s transcoding mode: SSI Operation - in 16 kbit/s transcoding mode, the ADPCM words are assigned to the I/O timeslot define d by ENB2 when SEL=1 and by ENB 1 when SEL= 0. See Fig ure 4. ST-BUS operation- in 16 kbit/s transcoding mode, the ADPCM words are assigned to the B2 timeslot when SEL=1 and to the B1 timeslot when SEL=0. See Figure 9.

15 A/µ

A-Law/µ−Law Select (Input). This input pin selects µ−Law comp anding when set to

logic 0, and A-Law companding when set t o logic 1. This control is for all channels .This input is ignored in Linear mode during which it may be tied to V

or VDD.

16 FORMAT FORMAT Selec t (Inpu t). Selects ITU-T P CM codin g when high and Sign-M agnit ude

PCM coding when low. This control is for all chann els.T his input is ignored in Linear

or VDD.

17 PWRDN

mode during which it may be tied to V Power-down (Input). An active low reset forcing the device into a low power mode

where all outputs are high-impedance and device operation is halted.

18 IC Internal Connection (Input). Tie to V

for normal operation.

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MT9126 Preliminary Information

Pin Description

Pin # Name Description

19 20 21

MS1 MS2 MS3

Mode Selects 1, 2 and 3 (Inputs). Mode selects for all four encoders.

MS3

MS2 MS1 MODE 0 0 0 32 kbit/s ADPCM 0 0 1 24 kbit/s ADPCM 0 1 0 16 kbit/s ADP CM in EN1/ENB 1 when SEL =0

in EN2/ENB2 when SEL=1 0 1 1 ADPCM Bypass for 32 kbit/s and 24 kbit/s 1 0 0 ADPCM Bypass for 16 kbit/s 1 0 1 PCM Bypass (64 kbit/s) to PCM1 if SEL=0, PCM2 if SEL=1 1 1 0 Algorithm reset (IT U-T opt ional reset) 1 1 1 ADPCMo disable

22 V

Positive Power Supply. Nominally 5 volts +/-10%

23 ADPCMi Serial ADPCM Stream ( Input). 128 kbit/s to 4096 kbit/s serial ADPCM word input

stream. Data bit s are clocked in on falling edge of BCLK in SS I mode and clo cke d in on the 3/4 bit edge of MCLK in ST-BUS mod e.

24 ADPCMo Serial ADPCM Stream (Output). 128 kbit/s to 4096 kbit/s serial ADPCM word outpu t

stream. Data bits are clocked out by rising edge of BCLK in SSI mode and clocked out by MCLK divided by two in ST-B US mode.

25 26 27

MS4 MS5 MS6

Mode Selects 4, 5 and 6 (Inputs). Mode selects for all four decoders.

MS6

MS5 MS4 MODE 0 0 0 32 kbit/s ADPCM 0 0 1 24 kbit/s ADPCM 0 1 0 1 6 kbit/s ADP CM in EN1/ENB 1 when SEL =0

in EN2/ENB2 when S EL=1 0 1 1 ADPCM Bypass for 32 kbit/s and 24 kbit/s 1 0 0 ADPCM Bypass for 16 kbit/s 1 0 1 P CM Bypass (64 kbit/s) to PCM1 if SEL=0, PCM2 if SEL=1 1 1 0 A lgo rithm reset (IT U-T opt ional reset) 1 1 1 PCMo1/2 disable

28 EN2 Enable Strobe 2 (Output). This 8 bit wide, active high strobe is acti ve during the B2

PCM channel in ST-BUS mode. Forced to high impedance when LINE AR=1.

Notes: All unused inputs should be connected to logic low or high unless otherwise stated. All outputs should be left open circuit when not used.

All inputs have TTL compatible logic levels except for MCLK which has CMOS compatible logic levels and PWRDN trigger compatible logic levels.

All outputs are CMOS with CMOS logic levels (See DC Electrical Characteristics).

which has Schmitt

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Preliminary Information MT9126

Functional Description

The Quad-channel ADPCM Transcoder is a low power, CMOS device capable of four encode and four decode operations per frame. Four 64 kbit/s channels (PCM octets) are compressed into four 32, 24 or 16 kbit/s ADPCM channels (ADPCM words), and four 32, 24 or 16 kbit/s ADPCM channels (ADPCM words) are expanded into four 64 kbit/s PCM channels (PCM octets). The ADPCM transcoding algorithm utilized conforms to ITU-T recommendation G.726 (excluding 40 kb/s), and ANSI T1.303 - 1989. Switching on-the-fly between 32 and 24 kbit/s transcoding is possible by toggling the appropriate mode select pins (supports T1 robbed-bit signalling).

All functions supported by the device are pin selectable. The four encode functions comprise a common group controlled via Mode Select pins MS1, MS2 and MS3. Similarily, the four decode functions form a second group commonly controlled via Mode Select pins MS4, MS5 and MS6. All other pin controls are common to the entire transcoder.

Serial (AD)PCM D ata I /O

Serial data transfer to/from the Quad ADPCM transcoder is provided through one ADPCM and two PCM ports (ADPCMi, ADPCMo, PCMi1, PCMo1, PCMi2, PCMo2). Data is transferred through these ports according to either ST-BUS or SSI requirements. The device determines the mode of operation by monitoring the signal applied to the F0i pin. When a valid ST-BUS frame pulse (244nSec low going pulse) is applied to the F0i will assume ST-BUS operation. If F0i continuously to V operation. Pin functionality in each of these modes is described in the following sub-sections.

ST-BUS Mode

During ST-BUS operation the C2o, EN1, EN2 and

outputs become active and all serial timing is

F0od derived from the MCLK (C4 BCLK inpu t i s tie d to V

the transcoder will assume SSI

. (See Figures 7, 8 & 9.)

Basic Rate “D” and “C” Chan nels

pin the transcoder

is tied

) and F0i inputs while the

The device requires 25 mWatts (MCLK= 4.096 MHz) typically for four channel transcode operation. A minimum master clock frequency of 4.096 MHz is required for the circuit to complete four encode channels and four decode channels per frame. For SSI operation a master clock frequency greater than

4.096 MHz and asynchronous, relative to the 8 kHz frame, is allowed.

The PCM and ADPCM serial busses support both ST-BUS and Synchronous Serial Interface (SSI) operation. This allows serial data clock rates from 128 kHz to 4096 kHz, as well as compatibility with Mitel’s standard Serial Telecom BUS (ST-BUS). For ST-BUS operation, on chip channel counters provide channel enable outputs as well as a 2048 kHz bit clock output which may be used by down-stream devices utilizing the SSI bus interface.

Linear coded PCM is also supported. In this mode the encoders compress, four 14-bit, two’s complement (S,S,S,12,...,1,0), uniform PCM channels into four 4, 3 or 2 bit ADPCM channels. Similarly, the decoder expands four 4, 3 or 2 bit ADPCM channels into four 16-bit, two’s complement (S,14,...,1 ,0), uniform PCM chann els. The da ta rate for both ST-BUS and SSI operation in this mode is 2048 kbit/s.

In ST-BUS mode, when ENB1 is brought low, transparent transport of the ST-BUS "Basic Rate Dand C-channels" is supported through the PCMi1 and PCMo1 pins. This allows a microprocessor controlled device, connected to the PCMi/o1 pins, to access the "D" and "C" channels of a transmission device connected to the ADPCMi/o pins. When ENB1 is brought high, the “D” and “C” channel outputs are tristated. Basic Rate “D” and “C” channels are not supported in LINEAR mode.(See Figure 7.)

SSI Mode

During SSI operation the BCLK, ENB1 and ENB2/ F0od

inputs become active. The C2o, EN1, and EN2 outputs are forced to a high-impedance state except during LINEAR operation during which the EN1 outp u t rema ins active. (See Figures 4, 5 & 6.)

The SSI port is a serial data interface, including data input and data output pins, a variable rate bit clock input and two input strobes providing enables for data transfers. There are three SSI I/O ports on the Quad ADPCM; the PCMi/o1 PCM port, the PCMi/o2 PCM port, and the ADPCMi/o port. The two PCM ports may transport 8-bit companded PCM or 16-bit linear PCM. The alignment of the channels is determined by the two input strobe signals ENB1 and ENB2/F0od strobes (ENB1 and ENB2/F0od

. The bit clock (BCLK) and input

) are common for all

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MT9126 Preliminary Information

three of the serial I/O ports. BCLK can be any frequency between 128 kHz and 4096 kHz synchronized to the input strobes. BCLK may be discontinuous outside of the strobe boundaries except when LINEAR=1. In LINEAR mode, BCLK must be 2048 kHz and continuous for 64 cycles after the ENB1 rising edge and for the duration of ENB2/

F0od

Mode Select Operation (MS1, MS2, MS3, MS4, MS5, MS6)

Mode Select pins MS1, MS2 and MS3 program different bit rate ADPCM coding, bypass, algorithmic reset and disable modes for all four encoder functions simultaneously. When 24 kbit/s ADPCM mode is selected bit 4 is unused while in 16 kb/s ADPCM mode all ADPCM channels are packed contiguously into one 8-bit octet. Mode Select pins MS4, MS5 and MS6 operate in the same manner for the four decode functions. The mode selects must be set up according to the timing const raints illustrated in Figures 16 and 17.

16 kbit/s ADPCM Mode

When SEL is set to 0, the 8-bit PCM octets of the B1, B2, B3 and B4 channels (PCMi1 and PCMi2) are compressed into four 2-bit ADPCM words on ADPCMo during t he EN B1 time slot i n SSI mo de a nd during the B1 timeslot in ST-BUS mode. Similarily, the four 2-bit ADPCM words on ADPCMi are expanded into four 8-bit PCM octets (on PCMo1 and PCMo2) during the ENB1/B1 times lot. (S ee Figu re s 4 & 7.)

When SEL is set to 1, The same conversion takes place as described when SEL = 0 except that the ENB2/B2 timeslots are utilized.

A-Law or µ-Law 8-bit PCM are received and transmitted most significant bit first starting with b7 and ending with b0. ADPCM data are most significant bit first starting with I1 and ending with I2.

ADPCM BYPASS (32 and 24 kbit/s)

32 kbit/s ADPCM Mode

In 32 kbit/ s ADPCM mode, the 8-bit PCM o ctets of the B1, B2, B3 and B4 channels (PCMi1 and PCMi2) are compressed into four 4-bit ADPCM words on ADPCMo. C o nv e rsel y, the 4-bit ADPC M words of the B1, B2, B3 and B4 channels from ADPCMi are expanded into four 8-bit PCM octets on PCMo1 and PCMo2. The 8-bit PCM octets (A-Law or µ-Law ) are transferred most significant bit first starting with b7 and ending with b0. ADPCM words are transferred most significant bit first starting with I1 and ending with I4 (See Figures 4 & 7). Reference ITU-T G .726 for I-bit definition s.

24 kbit/s ADPCM Mode

In 24 kbit/s mode PCM octets are transcoded into 3bit words rather than the 4-bit words utilized in 32 kbit/s ADPCM. This is useful in situations where lower bandwidth transmission is required. Dynamic operation of the mode select control pins will allow switching from 32 kbit/s mode to 24 kbit/s mode on a frame by frame basis. The 8 bit PCM octets (A-Law or µ-Law) are transferred most significant bit first starting with b7 and ending with b0. ADPCM words are transferred most significant bit first starting with I1 and ending with I3 (I4 becomes don’t care). (See Figures 4 & 7.)

In ADPCM bypass mode the B1 and B2 channel ADPCM words are bypassed (with a two-frame delay) to/from the ADPCM port and placed into the most significant nibbles of the PCM1/2 port octets. Note that the SEL pin performs no function for these two modes (See Figures 6 & 9). LINEAR, FORMAT and A/µ

In 32 kb/s ADPCM bypass mode, Bits 1 to 4 of the B1, B2, B3 and B4 channels from PCMi1 and PCMi2 are trans parently pas sed, with a two frame delay, to the same channels on ADPCMo. In the same manner, the B1, B2, B3 and B4 channels from ADPCMi are transparently passed, with a two frame delay, to the same channels on PCMo1 and PCMo2 pins. Bits 5 to 8 are don’t care. This feature allows two voice terminals, which utilize ADPCM transcoding, to communicate through a system without incurring unnecessary transcode conversions. This arrangement allows byte-wide or nibble-wide transport through a switching matrix.

24 kb/s ADPCM bypass mode is the same as 32 kb/s mode bypass excepting that only bits 1 to 3 are bypassed and bits 4 to 8 are don’t care.

pins are ignored in bypass mode.

ADPCM BYPASS (16 kbit/s)

When SEL is set to 0, only bits 1 and 2 of the B1, B2, B3 and B4 PCM octets (on PCMi1 and PCMi2) are bypassed, with a two frame delay, to the same channels on ADPCMo during the ENB1 timeslot in SSI mode and during the B1 timeslot in ST-BUS

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Preliminary Information MT9126

mode. Similarily, the four 2-bit ADPCM words on ADPCMi are transparently bypassed, with a two frame delay, to PCMo1 and PCMo2 during the ENB1 or B1 t i m eslot . Bits 3 - 8 are don’t c a re. (See Figures 6 & 9.)

When SEL is set to 1, the same bypass occurs as described when SEL = 0 except that the ENB2 or B2 timeslots are utilized.

LINEAR, FORMAT and A/µ

pins are ignored in

bypass mode.

PCM BYPASS

When SEL is set to 0, the B1 and B2 PCM channels on PCMi1 are transparently passed, with a twoframe delay, to the same channels on the ADPCMo. Simiarily, the two 8-bit words which are on ADPCMi are transparently passed, with a two-frame delay, to channels B1 and B2 of PCMo1 while PCMo2 is set to a high- impeda nce s tate.(See Figures 6 & 9.)

When SEL is set to 1, the B3 and B4 channels on PCMi2 are transparently passed, with a two frame delay, to the same channels on ADPCMo. Similarily, the two 8-bit words which are on ADPCMi are transparently passed, with a two-frame delay, to channels B3 and B4 of PCMo2. In this case PCMo1 is always high-impedance if ENB1 = 0. If E NB1 = 1 during ST-BUS operation then the D and C channels are active on PCMo1.

LINEAR, FORMAT and A/µ

pins are ignored in

bypass mode.

Algorithm Reset Mode

While an algorithmic reset is asserted the device will incrementally converge its internal variables to the 'Optional reset values' stated in G.726. Algorithmic reset requires that the master clock (MCLK) and frame pulse (ENB1/2 or F0i

) remain active and that the reset condition be valid for at least four frames. Note that this is not a power down mode; see PWRDN

for this fun c ti o n.

ADPCMo & PCMo1/2 Disable

When the decoders are programmed for PCMo1/2 disable (MS4 to MS6 set to 1) the PCMo1/2 outputs are high impedance during the B Channel timeslots and also, during ST-BUS operation, the D and C channel timeslots according to the state of ENB1. Therefore convergence is maintained. The encode processing function and data I/O remain active.

Whenever any combination of the encoders or decoders are set to the disable mode the following outputs remain active. A) ST-BUS mode: ENB2/

, EN1, EN2 and C2o. Also the “D” and “C”

F0od channels from PCMo1 and A DPCMo remain act ive if ENB1 is set to 0. If ENB1 is brought high then PCMo1 and ADPCMo are fully tri-stated. B) SSI mode: When used in the 16-bit linear mode, only the EN1 output remains active. For complet e chip power down see PWRDN

Other Pin Controls

16 Bit Linear PCM

Setting the LINEAR pin to logic one causes the device to change to 16-bit linear (uniform) PCM transmission on the PCMi/o1 and PCMi/o2 ports. The data rate for both S T-BUS and SSI operation in this mode is 2048 kbit/s and all decode and encode functions are aff ected by this pin. In SSI mode, the input channel strobes ENB1 and ENB2/F0od active for 8 cycles of BCLK for an ADPCM transfer. The EN1 output is high for one BCLK period at the end of the frame (i.e., during the 256

BCLK period). In ST-BUS mode, the output strobes EN1 and ENB2/ F0od

are adjusted to accommodate the required PCM I/O streams. The EN1 output becomes a single bit high true pulse during the last clock period of the frame (i.e., the 256 becomes a delayed, low true frame-pulse (F0od) output occuring during the 64

bit period) while ENB2/F0od

bit period after the

EN1 rising edge.

Linear PCM on PCMi1 and PCMi2, are received as 14-bit, two’s complement data with three bits of sign extension in the most significant positions (i.e., S,S,S,12,...1,0) for a total of 16 bits. The linear PCM data transmitted from PCMo1 and PCmo2 are 16-bit, two’s complement data with one sign bit in the most significa nt p os iti o n ( i.e ., S,14,13,...1 ,0 )

remain

When the encoders are programmed for ADPCMo disable (MS1 to MS3 set to 1) the ADPCMo output is set to a high impedance state and the internal encode function remains active. Therefore convergence is maintained. The decode processing function and data I/O remain active.

32 and 24 kbi t/s AD PCM mod e

In 32 kbit/s and 24 kbit/s linear mode, the 16-bit uniform PCM dual-oct ets of the B1, B2, B3 and B4 channels (from PCMi1 and PCMi2) are compressed into four 4-bit words on ADPCMo. The four 4-bit ADPCM words of the B1, B2, B3 and B4 channels

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