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.

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 ICH2. 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

 

Value

PCI

 

Value

Conf.

 

on

Conf.

 

on

Addr.

Register

Reset

Addr.

Register

Reset

00-01h

Vender ID

8086h

14-17h

Native Audio Bus Mstr. Addr.

1

02-03h

Device ID

2445h

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

 

 

Value

 

 

Value

 

 

Value

Offset

On

Offset

On

Offset

On

Addr. / Register

Reset

Addr. / Register

Reset

Addr. / Register

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

--

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

--

1Ch

Record Gain

8000h

34h

Reserved

--

0Ah

PC Beep Vol.

8000h

1Eh

Reserved

--

72h

Reserved

--

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

--

7Ch

Vender ID1

4144h

12h

CD Vol.

8808h

26h

Pwr Mgnt.

000xh

7Eh

Vender ID2

5340h

5-30Compaq Evo and Workstation Personal Computers

Featuring the Intel Pentium 4 Processor

Second Edition – January 2003

Page 117
Image 117
Compaq W4000 manual Audio Programming, Audio Configuration, Audio Control, AC’97 Audio Codec Control Registers