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Functional Description
5-106
82801AA and 82801AB Datasheet
5.17
ICH AC’97 2.1 Functional Description
This section describes the AC-link interface including an overview of the AC-link implementation
in the ICH and a detailed feature list of what is supported. Also included in this section is a
recommended feature list for AC’97 codecs. These are features that Intel recommends for a codec
designed for the ICH AC’97 controller.
For further information on the operation of the AC-link protocol, refer to the AC’97 specification.
References to AC’97 in this document refer to the AC’97 2.1 specification.
Note:
Poor performing PCI devices that cause long latencies (numerous retries) to CPU-to-PCI locked
cycles may starve isochronous transfers between USB or AC’97 devices and memory. This will
result in overrun or underrun, causing reduced quality of the isochronous data (e.g., audio).
The ICH supports the following features:
Independent PCI functions for audio and modem
Independent channels for PCM in and PCM out, microphone in
Left and right audio channels
Single modem line
16 bit sample resolution
Multiple sample rates
16 GPIOs
Dual codec configuration with two SDIN pins
Table 5-81
shows a detailed list of features supported by the ICH AC’97 digital controller.
Table 5-81. Featured Supported by ICH
Feature
Description
System Interface
Isochronous low latency bus master memory interface
Scatter/gather support for word-aligned buffers in memory
(all mono or stereo 16-bit data types are supported, no 8-bit data types are supported)
Data buffer size in system memory from 3 to 65535 samples per input
Data buffer size in system memory from 0 to 65535 samples per output
Independent PCI audio and modem functions with configuration and IO spaces
AC’97 codec registers are shadowed in system memory via driver (not PCI IO space)
AC’97 codec register accesses are serialized via semaphore bit in PCI IO space (new
accesses are not allowed while a prior access is still in progress)
Power
Management
Power management via ACPI control methods
Support for audio states: D0, D2, D3hot, D3cold
Support for modem states: D0, D3hot, D3cold
SCI event generation for PCI modem function with wake-up from D3cold
Independent codec D3 w/ Link down event, synchronized via two bit semaphore (in
PCI IO Space)