MAS3504D datasheet(17/40 Pages) MICRONAS

17 / 40 page

MAS 3504D

Micronas

3.5.2.1. Data Transmission Format

The codec is working on a page basis. That means,

that encoding and decoding is performed in blocks of

50 G.729 frames, whereas each frame consists of

10 bytes in byte swapped order (see Fig. 3–2). There-

fore most changes to the UserControl register become

effective when processing of a page is finished. The

pages are optionally preceeded by 10 byte header

frames (see Table 3–7).

Switching from encoding to decoding mode or vice

versa directly is not allowed. Instead the controller has

to send a stop request to the MAS 3504D (writing 0hex

to UserControl). Then the controller has to keep on

sending data in decoding mode or receive data in

encoding mode until the current page of 50 frames is

finished. After this run out time, the encoding or decod-

ing can be started again.

3.5.2.2. Encoder Operation

To enable the G.729 encoder mode, a special routine

has to be downloaded to the MAS 3504D IC first. This

has to be done with an I2C download before the

encoder is started the first time. If the encoder is

started without downloading the routine, the behavior

of the IC is unpredictable.

To switch to encoder operation mode, UserControl has

to be set to 3hex. Then 50 frames are encoded and

sent via the PIO interface. This is repeated until the

UserControl register is changed. If the transmission of

headers is enabled, each page of 50 frames is pre-

ceeded by a header frame as shown in Table 3–7.

To switch off the encoder, UserControl has to be set to

0hex. Then the encoding and sending of frames contin-

ues until the end of the current page and the operation

mode is set to stop.

3.5.2.3. Decoder Operation

The routines for the G.729 decoder mode are com-

pletely located in the MAS 3504D firmware. So there is

no need to download the encoder routine in a decode

only application.

To switch to decoder operation mode, UserControl has

to be set to 1hex. For decoding with slow speed, set

UserControl to 11hex. For decoding with fast speed, set

UserControl to 21hex. Then the decoder is requesting

several frames via the PIO interface to fill its internal

buffer. If enough data is available, 50 frames are

decoded. This is repeated until the UserControl regis-

ter is changed. If the transmission of headers is

enabled, a header frame (as shown in Table 3–7) has

to be sent before each page of 50 frames.

To switch off the decoder, UserControl has to be set to

0hex. Then the decoding of frames continues until the

end of the current page and the operation mode is set

to stop.

Table 3–6: Command Register Table

Address

(hex)

Mode

Function

Default

(hex)

Name

DC/DC operation control

8000

DCCF

r/w

Operation mode selection

UserControl

r/w

Output volume

7FFFF

Volume

r/w

Serial interface wordlength

Wordlength

r/w

Configuration of the I2S audio input interface

InputConfig

r/w

Configuration of the I2S audio output interface

4000

OutputConfig

r/w

Special operation options

HWControl

Table 3–7: Content of Page Header

Byte

345

8910

Value

[hex]

6D 72

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