MAS3504D datasheet(5/40 Pages) MICRONAS

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MAS 3504D

Micronas

1.2. Application Overview

The MAS 3504D can be applied in two major environ-

ments: as standalone decoder or as encoder/decoder

combination. For decoding only mode, the DAC 3550A

fits perfectly to the requirements of the MAS 3504D. It

is a high-quality multi sample rate DAC (8 kHz..

50 kHz) with internal crystal oscillator, which is only

needed for generating the decoder Clock, and inte-

grated stereo headphone amplifier plus two stereo

inputs.

1.2.1. Decoder Mode

In a memory-based voice playback environment, the

decoding is started with a command from a controller.

Then the MAS 3504D continuously requests frames of

G.729 data every 10 ms via the parallel (PIO) inter-

face.

A delayed response of the host to the request signal

(max.

20 milliseconds)

will

tolerated

the

MAS 3504D as long as the input buffer does not run

empty. A PC might use its DMA capabilities to transfer

the data in the background to the MAS 3504D without

interfering with its foreground processes.

The source of the bit stream may be a memory (e.g.

ROM, Flash) or PC peripherals, such as CD-ROM

drive, a hard disk or a floppy disk drive.

1.2.2. Encoder Mode

For encoding a support routine must be downloaded to

the MAS 3504D via I2C. After the encoder is started, it

begins to encode the incoming audio data and writes

the coded datastream to the parallel (PIO) interface.

A delayed response of the host to the data available

signal (max. 20 milliseconds) will be tolerated by the

MAS 3504D as long as the output buffer does not

overrun.

Fig. 1–2: Block diagram of a MAS 3504D, decoding a stored bit stream in a decoding only application

Fig. 1–3: Block diagram of a MAS 3504D in an encoding/decoding application

ROM, CD-ROM,

RAM, Flash Mem. ..

Host

(PC, Controller)

I2S

line out

I2C

demand signal

demand clock

G.729 bit stream

CLKI

CLKOUT

18.432 MHz

MAS 3504D

DAC

3550A

ROM, CD-ROM,

RAM, Flash Mem. ..

Host

(PC, Controller)

clock

line in

I2C

CLKI

G.729 bit stream

Mic in

Handshake signals

line out

strobe

data out

data in

I2S lines

MAS 3504D

PLL

AD/DA

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