Schematic Review Checklist
R
Intel
®
Pentium
®
4 Processor / Intel
®
850 Chipset Family Platform Design Guide 265
15.7.13 Intel
®
AC’97
Checklist Items Recommendations Reason/Impact
AC_SDOUT • Requires a jumper to 8.2 kΩ pull-up
resistor. Should not be stuffed for
default operation.
• This pin has a weak internal pull-
down. To properly detect a
safe_mode condition a strong pull-
up will be required to over-ride this
internal pull-down.
AC_SDIN[1],
AC_SDIN[0]
• Requires pads for weak 10 kΩ pull-
downs. Stuff resistor for unused
AC_SDIN signal or AC_SDIN signal
going to the CNR connector.
• If there is no codec on the system
board, then both AC_SDIN[1:0] should
be pulled down externally with
resisters to ground.
• AC_SDIN[1:0] are inputs to an
internal OR gate. If a pin is left
floating, the output of the OR gate
will be erroneous.
AC_BITCLK, • No extra pull-down resistors required. • When nothing is connected to the
link, BIOS must set a shut-off bit for
the internal keeper resistors to be
enabled. At that point, you do not
need pull-ups/pull-downs on any of
the link signals.
AC_SYNC • No extra pull-down resistors required. • Some implementations add
termination for signal integrity.
Platform specific.
15.7.14 Miscellaneous Signals
Checklist Items Recommendations Reason/Impact
SPKR • No extra pull-up resistors
• Effective Impedance due speaker and
codec circuitry must be greater than
50 k
Ω or a means to isolate the
resistive load from the signal while
PWROK is low be found.
• Has integrated pull-up of between
18 k
Ω and 42 kΩ. The integrated
pull-up is only enabled at boot/reset
for strapping functions; at all other
times, the pull-up is disabled.
• A low effective impedance may
cause the TCO Timer Reboot
function to be erroneously disabled.
TP[0] • Requires external pull-up resistor to
VccSUS3_3
• This signal is used for BATLOW in
Mobile.
• Not required for desktop.
FS[0] • Route to a test point. • ICH2 contains an integrated pull-up
for this signal. Test point used for
manufacturing appears in XOR
tree.
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