Figure 98. Audio Codecs; Figure 99. Audio And Audio/Modem Codecs - Intel Pentium 4 Design Manual

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Figure 98. Audio Codecs

Figure 99. Audio and Audio/Modem Codecs

The AC'97 interface can be routed using 5 mil traces with 5 mil space between the traces.
Maximum length between 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. Trace impedance should be Z
Intel has developed an advanced common connector for both AC'97 as well as networking
options. This is known as the Communication Network Riser (CNR).
Clocking is provided from the primary codec on the link via BITCLK, and is derived from a
24.576 MHz crystal or oscillator. Refer to the primary codec vendor for crystal or oscillator
requirements. BITCLK is a 12.288 MHz clock driven by the primary codec to the digital
controller (ICH2), and any other codec present. That clock is used as the timebase for latching and
driving data.
The ICH2 supports wake on ring from S1-S5 via the AC-link. The codec asserts SDATAIN to
wake the system. To provide wake capability and/or caller ID, standby power must be provided to
the modem codec.
® ®
Intel Pentium 4 Processor / Intel
AC'97 Digital
Link
ICH2
AC'97 D igital
Link
IC H2
= 60 Ω ± 15%
0
®
850 Chipset Family Platform Design Guide
I/O Controller Hub 2
AC'97
Audio
Codec
Audio Port
AC'97
Audio
Codec
Audio Port
AC97_2-audio-codecs
M odem Port
AC'97
Audio/
Modem
Codec
Audio Port
AC'97
Audio
Codec
Audio Port
A C97_A_A-M_codec
143