Confidential Draft
3/7/00
CS4281 Programming Manual
144
DS308PRM1
16.3
Sound Blaster Hardware Overview
The Sound Blaster block accepts commands and
data trapped by the PCI interface and passed along
by the Control Block. Mixer data and DSP
commands and data are translated to appropriate
reads and writes of the CS4281’s target registers
which set up the digital data path in the CS4281
and the analog path in the AC ‘97 part to
effectively emulate a Sound Blaster chip set.
The Sound Blaster Block supports both playback
and capture for DMA and PIO. Support is also
included for ADPCM through DMA-only
playback ADPCM 2:1, 3:1, and 4:1 decoding
(although 4:1 and 3:1 will play silence). Capture
ADPCM will not be supported. Other accesses
that set up the data paths through both the DSP
Cmd/Data and Mixer ports are also supported. The
SB hardware supports the same number of capture
and playback sample frequencies (mono and
stereo are considered one sample) from 6 kHz to
48 kHz.
16.4
Sound Blaster Mixer
This block communicates with the SB DSP block
as well as the PCI interface and AC-link. Some of
its data is required by the DSP and also a few DSP
commands such as Speaker On & Off configure
the AC ’97 codec.
16.4.1
Sound Blaster Mixer Mapping onto
the AC ‘97/CS4281 Mixer
The Sound Blaster Mixer is mapped onto the
AC ‘97 generic mixer and the digital portion on
board the CS4281 chip as described in the
following table. Since the AC ‘97 link supports
two codecs, the particular codec to update is
controlled through the
SSCR.MVCS
bit. When
SSCR.MVCS
is clear (default) the primary codec is
Register
D7
D6
D5
D4
D3
D2
D1
D0
00h
DATA RESET
02h
RESERVED
04h
VOICE VOLUME LEFT
1
VOICE VOLUME RIGHT
1
06h
RESERVED
08h
RESERVED
0Ah
X
X
X
X
MIC MIXING
1
0Ch
X
X
X
X
X
INPUT SELECT
X
0Eh
X
X
X
X
X
X
VSTC
X
20h
RESERVED
22h
MASTER VOLUME LEFT
1
MASTER VOLUME RIGHT
1
24h
RESERVED
26h
FM VOLUME LEFT
1
FM VOLUME RIGHT
1
28h
CD VOLUME LEFT
1
CD VOLUME RIGHT
1
2Ah
RESERVED
2Ch
RESERVED
2Eh
LINE VOLUME LEFT
1
LINE VOLUME RIGHT
1
40h - FFh
1
1
1
1
1
1
1
1
Table 12. Sound Blaster Mixer (indirect) registers
D
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ft
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