Chapter 5 Input/Output Interfaces
5-28
Compaq Deskpro EX Series of Personal Computers
First Edition – August 2000
5.8.5 AUDIO
PROGRAMMING
Audio subsystem programming consists configuration, typically accomplished during POST, and
control, which occurs during runtime. The register maps are described in the following
subsections.
5.8.5.1 Audio
Configuration
The audio subsystem is configured according to PCI protocol through the AC’97 audio controller
function of the 82801 ICH. Table 5-21 lists the PCI configuration registers of the audio subsystem.
Table 5–21
. AC’97 Audio Controller PCI Configuration Registers
Table 5-21.
AC’97 Audio Controller
PCI Configuration Registers (82801 Device 31/Function 5)
PCI
Conf.
Addr.
Register
Value
on
Reset
PCI
Conf.
Addr.
Register
Value
on
Reset
00-01h
Vender ID
8086h
14-17h
Native Audio Bus Mstr. Addr.
1
02-03h
Device ID
2415h
18-1Bh
Reserved
1h
04-05h
PCI Command
0000h
1C-2Bh
Reserved
1h
06-07h
PCI Status
0280h
2C-2Dh
Subsystem Vender ID
0000h
08h
Revision ID
XXh
2E-2Fh
Subsystem ID
0000h
09h
Programming
00h
30-3Bh
Reserved
--
0Ah
Sub-Class
01h
3Ch
Interrupt Line
00h
0Bh
Base Class Code
04h
3Dh
Interrupt Pin
02h
0Eh
Header Type
00h
3E-FFh
Reserved
0’s
10-13h
Native Audio Mixer Base Addr.
1
--
--
--
5.8.5.2 Audio
Control
The audio subsystem is controlled through a set of indexed registers that physically reside in the
audio codec . The register addresses are decoded by the audio controller and forwarded to the
audio codec over the AC97 Link Bus previously described. The audio codec’s control registers
(Table 5-22) are mapped into 64 kilobytes of variable I/O space.
Table 5–22. AC’97 Audio Codec Control Registers
Table 5-22.
AC’97 Audio Codec Control Registers
Offset
Addr. / Register
Value
On
Reset
Offset
Addr. / Register
Value
On
Reset
Offset
Addr. / Register
Value
On
Reset
00h Reset
0100h
14h Video Vol.
8808h
28h Ext. Audio ID.
0001h
02h Master Vol.
8000h
16h Aux Vol.
8808h
2Ah Ext. Audio Ctrl/Sts
0000h
04h Reserved
X
18h PCM Out Vol.
8808h
2Ch PCM DAC SRate
BB80h
06h Mono Mstr. Vol.
8000h
1Ah Record Sel.
0000h
32h PCM ADC SRate
BB80h
08h Reserved
X
1Ch Record Gain
8000h
34h Reserved
X
0Ah PC Beep Vol.
8000h
1Eh Reserved
X
72h Reserved
X
0Ch Phone In Vol.
8008h
20h Gen. Purpose
0000h
74h Serial Config.
7x0xh
0Eh Mic Vol.
8008h
22h 3D Control
0000h
76h Misc. Control Bits
0404h
10h Line In Vol.
8808h
24h Reserved
X
7Ch Vender ID1
4144h
12h CD Vol.
8808h
26h Pwr Mgnt.
000xh
7Eh Vender ID2
5340h
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