CMX7261 datasheet(45/64 Pages) CMLMICRO

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CMX7261 Voice Multi-transcoder

CMX7261

 2012 CML Microsystems Plc

Page 45

D/7261_FI-1.x/9

7.7.1

Normal Operation Overview

In normal operation (after the CMX7261 is configured), the required mode must be selected and correctly

formatted data input and read out. This process is carried out by selecting the transcoding type and

specifying the input audio source and output audio destination. Such options are required to be configured

correctly before transcoding/encoding/decoding can begin.

For continuous transcoding operation, data must be transferred into and out of the CMX7261. Audio

transfer into the CMX7261 can be through the analogue audio input, from an external PCM device, or the

host can feed in the data using C-BUS interface. Similarly, the transcoded output can be transferred out of

the CMX7261 using the analogue audio ouput, or using the PCM interface to an external PCM device or to

the host using the C-BUS interface. C-BUS transfers use the Audio In FIFO to transfer data into the

CMX7261, and the Audio Out FIFO to transfer data out of the CMX7261. The Status register is used to

indicate that the data has been dealt with. The CMX7261 can be configured to interrupt the host on FIFO

fill level or when it has read/written a specified number of samples from the Audio In/Out FIFOs.

In the process of transcoding the most significant registers are:



Mode - $6B write



IRQ Status - $7E read



IRQ Enable - $6C write



Audio In FIFO Data - $48, $49 write



Audio Out FIFO Data - $4C, $4D read



Audio In FIFO Level - $4B read



Audio Out FIFO Level - $4F read

7.7.2

Transcoder Operation

The many CMX7261 features provide significant flexibility however, basic encoding, decoding or

transcoding can be carried out easily by just understanding the operation of just a few registers.

Half-duplex transcoder operation is illustrated by Figure 27 and the following detailed example.

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