Intel 820E Benutzerhandbuch

Design Guide 

 

85 

The ICH2 implements an AC’97 2.1-compliant digital controller. Any codec attached to the ICH2  
AC-link also must be AC’97 2.1 compliant. Please contact your codec IHV for information on 
2.1-compliant products. The AC’97 2.1 specification is on the following Intel web page:  

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 serially. 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. The following figure shows a two-codec topology of 
the AC-link for the ICH2. 

AC '97 2.1

controller section

of ICH2

Digital AC '97

2.1 controller

Primary codec

Secondary codec

AC / MC

AC / MC / AMC

ICH2_AC97_codec_conn

SDIN 0

SDIN 1

RESET#

SDOUT

SYNC

BIT_CLK

 

The AC’97 interface can be routed using 5 mil traces, with 5 mil space between traces. The maximum 
length from ICH2 to CODEC/CNR is 14 inches, in a tee topology. This assumes that a CNR riser card 
implements its audio solution with a maximum trace length of 4 inches for the AC-link. The trace 
impedance should be as follows: Z

0

 = 60 

Ω

 ± 15%.