Intel
82801BA ICH2 Datasheet
5-133
Functional Description
Note:
Throughout this document, references to D31:F5 indicate that the audio function exists in PCI
Device 31, Function 5. References to D31:F6 indicate that the modem function exists in PCI
Device 31, Function 6.
5.18.1
AC-link Overview
The ICH2 is an AC’97 2.1 compliant controller that communicates with companion codecs via a
digital serial link called the AC-link. All digital audio/modem streams and command/status
information is communicated over the AC-link.
The AC-link is a bi-directional, serial PCM digital stream. It handles multiple input and output data
streams, as well as control register accesses, employing a time division multiplexed (TDM)
scheme. The AC-link architecture provides for data transfer through individual frames transmitted
in a serial fashion. Each frame is divided into 12 outgoing and 12 incoming data streams, or slots.
The architecture of the ICH2 AC-link allows a maximum of two codecs to be connected.
Figure 5-20
shows a two codec topology of the AC-link for the ICH2.
PCI Modem
function
Read/write access to modem codec registers 3Ch-58h and vendor registers 5Ah–7Eh
16-bit mono modem line1 output and input, up to 48 kHz (slot 5)
Low latency GPIO[13:11,8:6,4:3,1:0] via hardwired update between slot 12 and PCI
IO register
Programmable PCI interrupt on modem GPIO input changes via slot 12 GPIO_INT
SCI event generation on primary or secondary SDIN wake-up signal
AC-link
AC’97 2.1 compliant AC-link interface
Variable sample rate output support via AC’97 SLOTREQ protocol (slots
3,4,5,6,7,8,9)
Variable sample rate input support via monitoring of slot valid tag bits (slots 3,4,5,6)
3.3 V digital operation meets AC’97 2.1 DC switching levels
AC-Link IO driver capability meets AC‘97 2.1 dual codec specifications
Codec register status reads must be returned with data in the next AC-link frame, per
AC’97 2.1 specification.
Multiple Codec
Dual codec addressing: All AC’97 codec register accesses are addressable to codec
ID 00 (primary) or codec ID 01 (secondary)
Dual codec receive capability via primary and secondary SDIN pins
(primary, secondary SDIN frames are internally validated, synchronized, and OR’d)
Figure 5-19. ICH2 Based AC’97 2.1
Table 5-89. Featured Supported by ICH2 (Continued)
Feature
Description
Audio In (Record)
Audio Out (Playback)
Modem
PC
Mic.
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