CS4281 Programming Manual
DS308PRM1
161
Confidential Draft
3/7/00
17.5
SB Configuration Setup
Requirements
• Use Environment BLASTER Variable to
determine which DMAn (0-3) to use as Legacy
• Setup legacy DMAn (CCLS, PC/PCI, DDMA,
and Polled operation);
IOTCR.DMA[1:0]
= n
•
Set FIFOn size to minimum (2-4 samples);
FCRn.SZ[7:0]
•
Turn on Legacy DMA engine (will set
Mask);
DMRn.DMA
•
Set SB format: only DMRn format bits on:
CBC, SWAPC, USIGN, SIZE8
-
MONO
function is controlled internally by
SB engine, based on game-programmed
format
-
DMA/POLL
and
DMRn.TR[1:0]
functions will
also be controlled directly by SB engine
•
Set
FCRn.DACZ
•
Clear
FCRn.PSH
(required for SB silence
command 80h)
•
Enable FIFOm;
FCRn.FEN
•
Initialize Upper Base Count and Upper
Address Count to 0
• Interrupt Setup - check environment BLASTER
variable
•
Mask unused interrupts (usually all but
SBINT); HIMR
•
Optionally switch from PCI to ISA
interrupts; HIMR, IIER
• Turn on Sound Blaster and FM;
SSCR.SB
= 1,
SSPM.FMEN
= 1.
• Disable Host Interrupts from legacy DMA;
DCRn interrupt enable bits = 0
• Setup and turn on legacy I/O trapping for SB,
FM, and Game Port; IOTSB, IOTFM, and
IOTGP
• If PC/PCI, set up PC/PCI registers and I/O Trap
for PC/PCI; IOTPCP and
PCPCR.PCPEN
set
• Select, setup, and turn on legacy I/O trapping
for DMA (plus global trapping); IOTCR
• Setup CSRC and PSRC slot mapping (between
AC link and FIF0m); SRCSA
•
NOTE: SRCSA mapping will be loaded
into the FIFO slot mapping in FCRm when
SB playback or record is enabled.
• Enable SRCs;
SSPM.PSRCEN
and
SSPM.CSRCEN
set.
• Do SB Reset to setup mixer registers
• Set AC Link Output Slot Valid bits in ACOSV
• Make sure Codec is powered up and
ADC/DAC running in proper mode (sets
ACISV or ACISV2 valid bits).
• Write Codec DAC volume to 0 dB (Index 18h =
0808h). SB uses CS4281 registers for Voice
volume
When exiting Sound Blaster mode (tear-down):
• Sound Blaster Voice Volume unmuted, 0 dB;
PPLVC/PPRVC = 0
• Turn off Sound Blaster;
SSCR.SB
= 0
• Disable legacy I/O trapping;
IOTCR.ITD
= 1
• Disable legacy DMA
SB Input Select (0Ch)
SB Value
(Hex)
AC ‘97 1Ah Register
(Hex)
Mic Source (default)
0
0000h
CD Source
1
0101h
Mic Source
2
0000h
Line-In Source
3
0404h
Table 25. Sound Blaster Input Select
D
ra
ft
Содержание CS4281
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