Table of Contents
Chapter 5 Input/Output Interfaces
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
PCI
Conf.
Addr.
Register
00-01h
Vender ID
02-03h
Device ID
04-05h
PCI Command
06-07h
PCI Status
08h
Revision ID
09h
Programming
0Ah
Sub-Class
0Bh
Base Class Code
0Eh
Header Type
10-13h
Native Audio Mixer Base Addr.
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
Offset
Addr. / Register
00h Reset
02h Master Vol.
04h Reserved
06h Mono Mstr. Vol.
08h Reserved
0Ah PC Beep Vol.
0Ch Phone In Vol.
0Eh Mic Vol.
10h Line In Vol.
12h CD Vol.
5-28 Compaq Deskpro EX Series of Personal Computers
Table 5-21.
AC'97 Audio Controller
PCI Configuration Registers (82801 Device 31/Function 5)
Reset
8086h
2415h
0000h
0280h
Table 5-22.
AC'97 Audio Codec Control Registers
Value
On
Offset
Reset
Addr. / Register
0100h
14h Video Vol.
8000h
16h Aux Vol.
X
18h PCM Out Vol.
8000h
1Ah Record Sel.
X
1Ch Record Gain
8000h
1Eh Reserved
8008h
20h Gen. Purpose
8008h
22h 3D Control
8808h
24h Reserved
8808h
26h Pwr Mgnt.
First Edition – August 2000
Value
PCI
on
Conf.
Addr.
Register
14-17h
Native Audio Bus Mstr. Addr.
18-1Bh
Reserved
1C-2Bh
Reserved
2C-2Dh
Subsystem Vender ID
XXh
2E-2Fh
Subsystem ID
00h
30-3Bh
Reserved
01h
3Ch
Interrupt Line
04h
3Dh
Interrupt Pin
00h
3E-FFh
Reserved
1
--
--
Value
On
Offset
Reset
Addr. / Register
8808h
28h Ext. Audio ID.
8808h
2Ah Ext. Audio Ctrl/Sts
8808h
2Ch PCM DAC SRate
0000h
32h PCM ADC SRate
8000h
34h Reserved
X
72h Reserved
0000h
74h Serial Config.
0000h
76h Misc. Control Bits
X
7Ch Vender ID1
000xh
7Eh Vender ID2
Value
on
Reset
1
1h
1h
0000h
0000h
--
00h
02h
0's
--
Value
On
Reset
0001h
0000h
BB80h
BB80h
X
X
7x0xh
0404h
4144h
5340h
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