SM5902AF Datasheet, PDF (23/40 Pages) Nippon Precision Circuits Inc – compression and non compression type shock-proof memory controller

SM5902AF
Shock-proof operation overview
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.
- 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 ADPCM 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.
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