Design Guide

Platform Design Checklist
R
304 Intel
®
855GM/855GME Chipset Platform Design Guide
16.7.5. AC ’97 Interface
Pin Name System
Pull-up/Pull-down
Series
Termination
Resistor
Notes
9
AC_BIT_CLK
None
33-47
Ω
The internal pull-down resistor is controlled by the AC’97
Global Control Register, ACLINK Shut Off bit:
1 = enabled; 0 = disabled
When no AC'97 devices are connected to the link, BIOS
must set the ACLINK Shut Off bit for the internal keeper
resistors to be ENABLED. At that point, pull-ups/pull-
downs are NOT needed on ANY of the link signals.
AC_SDATAIN[2:0]
None
33-47
Ω
A series termination resistor is required for the
PRIMARY CODEC.
A series termination resistor is required for the
SECONDARY and TERTIARY CODEC if the resistor is
not found on CODEC.
AC_SDATAOUT
None
33-47
Ω
A series termination resistor is required for the
PRIMARY CODEC.
One series termination resistor is required for the
SECONDARY/ TERTIARY CODEC connector card if the
resistor is not found on the connector card.
AC_SYNC
None
33-47
Ω
A series termination resistor is required for the
PRIMARY CODEC.
One series termination resistor is required for the
SECONDARY/ TERTIARY CODEC connector card if the
resistor is not found on the connector card.