VS1011 Datasheet, PDF (32/43 Pages) List of Unclassifed Manufacturers – MP3 AUDIO CODEC

VLSI
Solution ^y
VS1011 PRELIMINARY
VS1011
9. OPERATION
9 Operation
9.1 Clocking
VS1011 operates on a single, nominally 24.576 MHz fundamental frequency master clock. This clock
can be generated by external circuitry (connected to pin XTALI) or by the internal clock chrystal interface
(pins XTALI and XTALO). This clock is sufficient to support a high quality audio output for almost all
standard sample rates and bit-rates (see Application Notes for VS10XX).
9.2 Hardware Reset
When the XRESET -signal is driven low, VS1011 is reset and all the control registers and internal states
are set to the initial values. XRESET-signal is asynchronous to any external clock. The reset mode
doubles as a full-powerdown mode, where both digital and analog parts of VS1011 are in minimum
power consumption stage, and where clocks are stopped. Also XTALO and XTALI are grounded.
After a hardware reset (or at power-up), the user should set such basic software registers as SCI VOL
for volume (and SCI CLOCKF if the input clock is anything else than 24.576 MHz) before starting
decoding.
9.3 Software Reset
In some cases the decoder software has to be reset. This is done by activating bit 2 in SCI MODE register
(Chapter 8.6.1). Then wait for at least 2 µs, then look at DREQ. DREQ will stay down for at least 6000
clock cycles, which means an approximate 250 µs delay if VS1011 is run at 24.576 MHz. After DREQ
is up, you may continue playback as usual.
If you want to make sure VS1011 doesn’t cut the ending of low-bitrate data streams and you want to do
a software reset, it is recommended to feed 2048 zeros to the SDI bus after the file and before the reset.
9.4 Play/Decode
This is the normal operation mode of VS1011. SDI data is decoded. Decoded samples are converted to
analog domain by the internal DAC. If there are bad problems in the decoding process, the error flags of
SCI HDAT0 and SCI HDAT1 are set to 0 and analog outputs are muted.
When there is no input for decoding, VS1011 goes into idle mode (lower power consumption than during
decoding) and actively monitors the serial data input for valid data.
Version 0.71, 2004-07-20
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