>From the compaq EN PIII technical ref manual:
5.8 AUDIO SUBSYSTEM
A PCI audio subsystem is integrated onto the system board of all Compaq
Deskpros covered in
this guide. Implementing AC’97 design guidelines, the audio subsystem
features Compaq
Premier Sound components designed to provide optimum sound. Key features
of the audio
subsystem include:
♦ AC’97 ver. 2.1 compliance
♦ Multiple audio channel streaming
♦ Soft CD, DVD/AC-3 processing
♦ Wavetable synthesis utilizing system memory
♦ Acoustic echo cancellation
♦ 16-bit stereo PCM input and output w/ up to 48 KHz sampling
♦ Compaq Premier Sound components
5.8.1 FUNCTIONAL ANALYSIS
A block diagram of the audio subsystem is shown in Figure 5-9. The
architecture uses the AC’97
Audio Controller of the 82801 ICH component to access and control an
Analog Devices AD1881
Audio Codec, which provides the analog-to-digital (ADC) and
digital-to-analog (DAC)
conversions as well as the mixing functions.
.....
5.8.2 AC97 AUDIO CONTROLLER
The AC97 Audio Controller is a PCI device (device 31/function 5) that is
integrated into the
82801 ICH component and supports the following functions:
♦ Read/write access to audio codec registers
♦ 16-bit stereo PCM output @ up to 48 KHz sampling
♦ 16-bit stereo PCM input @ up to 48 KHz sampling
♦ Acoustic echo correction for microphone
♦ AC’97 Link Bus
♦ ACPI power management
5.8.3 AC97 LINK BUS
The audio controller and the audio codec communicate over a five-signal
AC97 Link Bus (Figure
5-10). The AC97 Link Bus includes two serial data lines (SD OUT/SD IN)
that transfer control
and PCM audio data serially to and from the audio codec using a
time-division multiplexed
(TDM) protocol. The data lines are qualified by a 12.288 MHz BIT_CLK
signal driven by the
audio codec. Data is transferred in frames synchronized by the 48-KHz
SYNC signal, which is
derived from the clock signal and driven by the audio controller. The
SYNC signal is high during
the frame’s tag phase then falls during T17and remains low during the
data phase. A frame
consists of one 16-bit tag slot followed by twelve 20-bit data slots.
When asserted (typically
during a power cycle), the RESET- signal (not shown) will reset all
audio registers to their
default values.
T1 T2 T3 T18 T19
T38 T39 T58
BIT_CLK
(12.288 MHz)
SYNC
(48 KHz)
Codec Bit 15 Bit 14
SD OUT Bit 0 Bit 19 Bit 18
Bit 0 Bit 19 Bit 18 Bit 0 Bit 19
Ready
or SD IN
Slot 0 Slot 1
Slot 2
(Tag) (Data)
(Data)
Slot Description
0 Bit 15: Frame valid bit
Bits 14-3: Slots 1-12 valid bits
Bits 2-0: Codec ID
1 Command address: Bit 19, R/W; Bits 18..12, reg.
Index; Bits 11..0, reserved.
2 Command data
3 Bits 19-4: PCM audio data, left channel (SD OUT,
playback; SD IN, record)
Bits 3-0 all zeros
4 Bits 19-4: PCM audio data, right channel (SD OUT,
playback; SD IN, record)
Bits 3-0 all zeros
5 Modem codec data (not used in this system)
6-11 Reserved
12 I/O control
Figure 5-10. AC’97 Link Bus Protocol
--
no output sound on ubuntu 9 (compaq CQ40)
https://bugs.launchpad.net/bugs/400231
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