Intel Pentium 4 User Manual

I/O Controller Hub 2
R
Intel
®
Pentium
®
4 Processor / Intel
®
850 Chipset Family Platform Design Guide 147
Figure 103. CDC_DN_ENAB# Support for Two-Codecs on Motherboard / Two-Codecs on CNR
Codec A
RESET#
SDATA_IN
Codec C
RESET#
SDATA_ IN
AC97_RESET#
Vcc
CDC_DN_ENAB#
CNR BoardMotherboard
R
A
10kohms
R
B
1kohms
To General
Purpose Input
From AC '97
Controller
CNR Connector
To AC '97
Digital
Controller
SDATA_IN0
SDATA_IN1
Codec D
RESET#
SDATA_ IN
Codec B
RESET#
SDATA_IN
Circuit Notes
• All CNR designs include resistor R
B
. The value of R
B
is either 1 kΩ or 100 kΩ, depending on
the intended functionality of the CNR (whether or not it intends to be the primary/controlling
codec).
• Any CNR with two codecs must implement R
B
with value 1 kΩ. If there is one Codec, use a
100 kΩ pull-up resistor. A CNR with zero codecs must not stuff R
B
. If implemented, R
B
must
be connected to the same power well as the codec so that it is valid whenever the codec has
power.
• A motherboard with one or more codecs down must implement R
A
with a value of 10 kΩ.
• The CDC_DN_ENAB# signal must be run to a GPI so that the BIOS can sense the state of the
signal. CDC_DN_ENAB# is required to be connected to a GPI; a connection to a GPIO is
strongly recommended for testing purposes.
Table 34. Signal Descriptions
Signal Description
CDC_DN_ENAB# When low, indicates that the codec on the motherboard is enabled and primary on the
AC97 Interface. When high, indicates that the motherboard codec(s) must be
removed from the AC ’97 Interface (held in reset), because the CNR codec(s) will be
the primary device(s) on the AC ’97 Interface.
AC97_RESET# Reset signal from the AC ’97 Digital Controller (ICH2).
SDATA_INn AC ’97 serial data from an AC ’97-compliant codec to an AC ’97-compliant controller
(i.e., the ICH2).

Intel Pentium 4 Specifications

General

Brand	Intel
Model	Pentium 4
Category	Computer Hardware
Language	English