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CS4281 Programming Manual
DS308PRM1
145
Confidential Draft
3/7/00
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
Hardware Volumes and are:
•
MVCS
- Selects Primary (0) or Secondary (1)
AC ‘97 codec.
•
MVLD
- Master Volume Line-Out Disable. When
set, register 0x02 is NOT updated.
•
MVAD
- Master Volume Alternate/Headphone
Disable. When set, register 0x04 is NOT
updated.
•
MVMD
- Master Volume Mono Out Disable.
When set, register 0x06 is NOT updated.
The Sound Blaster mixer supports independent
volume controls for the FM and the PCM (PSRC)
path. Since the CS4281 mixes FM digitally before
sending the data to the AC Link, independent
controls for PCM (voice) and FM are provided
prior to mixing.
The CS4281 will write the appropriate volume to
the Master Input Volume depending on which
input is selected by the Input Setting Register.
The Input Select to AC Link translations are in
Table 25.
The mapping of the Sound Blaster Mixer into the
CS4281/AC ‘97 mixer is drawn out schematically
SB Pro Mixer Read Table
Mixer Index
Data Returned
0
*last data read
2
[22h]
4
[04h]
6
[26h]
8
[28h]
0Ah
[0Ah]
0Ch
[0Ch]
0Eh
[0Eh]
20h
11h
22h
[22h]
24h
*last data read
26h
[26h]
28h
[28h]
2Ah
*last data read
2Ch
*last data read
2Eh
[2Eh]
40h - FFh
FFh
* return the same thing as the previous SB mixer data register read
[n] - contents of mixer register n
Mixer Index bits 0 and 4 are don’t cares and alias to the above locations
Table 13. SB Pro Mixer - All Read Values
D
ra
ft
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