Confidential Draft
3/7/00
CS4281 Programming Manual
158
DS308PRM1
17.3
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 com-
mands 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 emu-
late a Sound Blaster chip set.
The Sound Blaster Block supports both playback
and capture for DMA and PIO. Support is also in-
cluded 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 consid-
ered one sample) from 6 kHz to 48 kHz.
17.4
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.
17.4.1
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 follow-
ing 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 selected. When
SSCR.MVCS
is set, the secondary codec is selected.
The SB Master Volume data can to be written to all
three AC ‘97 Master Volume controls since the
Sound Blaster user might be using any or all of
these outputs to listen to his game audio. Master
volume translation is controlled through the Sound
System Control Register (SSCR). This register
contains bits that determine which AC ‘97 codec to
update (primary or secondary) and which volumes
on that codec to update. The bits in SSCR control
master volume updates for SB Master and Hard-
ware Volumes and are:
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 21. Sound Blaster Mixer (indirect) registers
D
ra
ft
Содержание CS4281
Страница 8: ...Confidential Draft 3 7 00 CS4281 Programming Manual 8 DS308PRM1 D r a f t...
Страница 12: ...Confidential Draft 3 7 00 CS4281 Programming Manual 12 DS308PRM1 D r a f t...
Страница 24: ...Confidential Draft 3 7 00 CS4281 Programming Manual 24 DS308PRM1 D r a f t...
Страница 34: ...Confidential Draft 3 7 00 CS4281 Programming Manual 34 DS308PRM1 D r a f t...
Страница 44: ...Confidential Draft 3 7 00 CS4281 Programming Manual 44 DS308PRM1 D r a f t...
Страница 114: ...Confidential Draft 3 7 00 CS4281 Programming Manual 114 DS308PRM1 D r a f t...
Страница 192: ...Confidential Draft 3 7 00 CS4281 Programming Manual 192 DS308PRM1 D r a f t...