VS1002D Datasheet, PDF (27/54 Pages) List of Unclassifed Manufacturers – MP3 AUDIO CODEC

VLSI
Solution ^y
VS1002d
VS1002D
8. FUNCTIONAL DESCRIPTION
If SM TESTS is set, SDI tests are allowed. For more details on SDI tests, look at Chapter 9.7.
SM STREAM activates VS1002d’s stream mode. In this mode, data should be sent with as even intervals
as possible (and preferable with data blocks of less than 512 bytes), and VS1002d makes every attempt
to keep its input buffer half full by changing its playback speed upto 5%. For best quality sound, the
average speed error should be within 0.5%, the bitrate should not exceed 160 kbit/s and VBR should not
be used. For details, see Application Notes for VS10XX.
SM PLUSV activates MP3+V decoding. Without this bit set, only MP3 decoding is performed even for
files with additional PlusV data.
SM DACT defines the active edge of data clock for SDI. If clear data is read at the rising edge, and if set
data is read at the falling edge.
When SM SDIORD is clear, bytes on SDI are sent as a default MSb first. By setting SM SDIORD, the
user may reverse the bit order for SDI, i.e. bit 0 is received first and bit 7 last. Bytes are, however, still
sent in the default order. This register bit has no effect on the SCI bus.
Setting SM SDISHARE makes SCI and SDI share the same chip select, as explained in Chapter 7.2, if
also SM SDINEW is set.
Setting SM SDINEW will activate VS1002 native serial modes as described in Chapters 7.2.1 and 7.4.2.
Note, that this bit is set as a default when VS1002d is started up.
By activating SM ADPCM and SM RESET at the same time, the user will activate IMA ADPCM record-
ing mode. More information is available in document Application Notes for VS10XX.
If SM ADPCM HP is set at the same time as SM ADPCM and SM RESET, ADPCM mode will start
with a high-pass filter. This may help intelligibility of speech when there is lots of background noise.
The difference created to the ADPCM encoder frequency response is as shown in Figure 13.
VS1002 AD Converter with and Without HP Filter
5
No High−Pass
High−Pass
0
−5
−10
−15
−20
0
500
1000
1500
2000
2500
3000
3500
4000
Frequency / Hz
Figure 13: ADPCM Frequency Responses.
Version 1.0, 2005-04-27
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