Ac '97 Interface - Intel 855PM Design Manual

R
14.8.5.

AC '97 Interface

Pin Name
Pull up/Pull down
AC_BIT_CLK
AC_SDIN[2:0]
AC_SDOUT
AC_SYNC
®
Intel 855PM Chipset Platform Design Guide
ICH4-M AC '97 Interface – Resistor Recommendations
System Series
Termination
Resistor
33 - 47 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.
See Section 9.3 for routing requirements
33 - 47 A series termination resistor (R1) is required for
the PRIMARY CODEC.
A series termination resistor is required for the
SECONDARY (R2=R1) and TERTIARY
(R3=R1) CODEC if the resistor is not found on
CODEC.
See Section 9.3 for routing requirements.
33 - 47 A series termination resistor is required for the
PRIMARY CODEC.
One series termination resistor (R2=R1) is
required for the SECONDARY/ TERTIARY
CODEC connector card if the resistor is not
found on the connector card.
See Section 9.3 for routing requirements.
33 - 47 A series termination resistor is required for the
PRIMARY CODEC.
One series termination resistor (R2=R1) is
required for the SECONDARY/ TERTIARY
CODEC connector card if the resistor is not
found on the connector card.
See Section 9.3 for routing requirements.
Platform Design Checklist
Notes
311