CMX7261 datasheet(21/64 Pages) CMLMICRO

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CMX7261 Voice Multi-transcoder

CMX7261

 2012 CML Microsystems Plc

Page 21

D/7261_FI-1.x/9

General Description

6.1

CMX7261 Features

The CMX7261 is a multi-transcoder chip that performs encoding and decoding of PCM, CVSD and

G.729A, as well as transcoding between these standards. The CMX7261 can be operated either as a half

duplex or as a full duplex transcoder. Full duplex operation means that a type of transcoding may be

specified on one channel and the opposite transcoding will then be implemented on a second audio

stream.

A flexible power control facility allows the device to be placed in its optimum powersave mode when not

actively processing signals.

The device includes a crystal clock generator, with phase locked loop to enable operation from a range of

reference xtal frequencies.

Block diagrams of the device are shown in Figure 1.

Encoder Functions:



Analogue voice to PCM encoding (

μ-law or A-law according to G.711 standard).



Analogue voice to CVSD encoding.



Analogue voice to G.729A encoding.



Input filtering on the input signal

– when the signal comes from CMX7261’s analogue audio input.

Decoder Functions:



PCM decoding to analogue voice.



CVSD decoding to analogue voice.



G.729A decoding to analogue voice.



Output filtering on the output signal

– when the signal is being sent to CMX7261’s analogue audio

output.

Transcoder Functions (Half-Duplex):



PCM to CVSD transcoding.



PCM to G.729A transcoding.



G.729A to CVSD transcoding.



CVSD to G.729A transcoding



PCM

μ / A / linear to PCM μ / A / linear transcoding.



Transcoding between any of, analogue audio / CVSD / G.729A / G.711 A-law / G.711

μ-law is

possible.

Transcoder Functions (Full-Duplex):



Two separate audio streams (channel-1, channel-2) are processed simultaneously.



Channel-1 may process audio using a Decoder, Encoder or Transcoder function.



Channel-2 will process audio in the reverse manner to channel-1. For example, if channel-1 is

configured to transcode from CVSD to G.729A, channel-2 will transcode from G.729A to CVSD.

Interface:



Optimised C-BUS (4-wire, high speed synchronous serial command/data bus) interface to host for

control and data transfer, including streaming C-BUS for efficient data transfer.



Input data can come through the analogue audio input or, C-BUS or from an external PCM device

connected to CMX7261

’s PCM port.



Output data can be sent to the analogue audio output or, C-BUS or, to an external PCM device

connected to CMX7261

’s PCM port.



Open drain IRQ to host.



Three GPIO pins.



Serial memory or C-BUS (host) boot mode.

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