Ac '97 Interface - Intel 855GM Design Manual

Platform Design Checklist
16.7.5.

AC '97 Interface

Pin Name
Pull-up/Pull-down
AC_BIT_CLK None
AC_SDATAIN[2:0] None
AC_SDATAOUT None
AC_SYNC None
304
System Series
Termination
Resistor
33-47 Ω
33-47 Ω
33-47 Ω
33-47 Ω
Notes
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.
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.
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.
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.
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Intel 855GM/855GME Chipset Platform Design Guide
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