SM5859AF datasheet(21/33 Pages) NPC

21 / 33 page

SM5859AF

NIPPON PRECISION CIRCUITS-21

Shock-proof mode is the mode that realizes shock-

proof operation using external DRAM. Shock-proof

mode is invoked by setting MSON=H in microcon-

troller command 80H.

This mode comprises the following 3 sequences.

Shock-proof operation overview

- Encode sequence

1. Input data from a signal processor IC is stored in

internal buffers.

2. Encoder starts after a fixed number of data have

been received.

3. The encoder, after the most suitable predicting

filter type and quantization steps have been deter-

mined, performs APC encoding and then writes to

external DRAM.

- Decode sequence

1. Reads compressed data stored in external buffer

RAM at rate fs.

2. Decoder starts, using the predicting filter type

and quantization levels used when encoded.

3. Performs attenuation operation (including muting

operation)

4. Outputs the result.

- Compare-connect sequence

1. Encoding immediately stops when either external

buffer RAM overflows or when a CD read error

occurs due to shock vibrations.

2. Then, using microcontroller command 80H, the

compare-connect start command is executed and

compare-connect sequence starts.

3. Compares data re-read from the CD with the pro-

cessed final valid data stored in RAM (confirms its

correctness).

4. As soon as the comparison detects conforming

data, compare-connect sequence stops and

encode sequence re-starts, connecting the data

directly behind previous valid data.

SM5859AF Datasheet(PDF) 21 Page - Nippon Precision Circuits Inc