
82801AA and 82801AB Datasheet
2-9
Signal Description
2.10
SMBus Interface
This is accessed from the PCI Device 31:Function 3.
Note:
Although this is called the SMBus logic, it has capability to access slaves that are I
2
C compatible.
2.11
System Management Interface
2.12
Real Time Clock Interface
Table 2-10. SM Bus Interface Signals
Name
Type
Description
SMBDATA
I/OD
SMBus Data:
External pull-up is required.
SMBCLK
I/OD
SMBus Clock:
External pull-up is required.
SMBALERT#/
GPIO[11]
I
SMBus Alert:
This signal is used to wake the system or generate SMI#. If not
used for SMBALERT#, it can be used as GPIO[11].
Table 2-11. System Management Signal
Name
Type
Description
INTRUDER#
I
Intruder Detect:
Disables system if box detected open. If this signal is not connected
to a switch, the software can directly read the state of the input and use it as a GPI.
ALERTCLK
GPIO[27]
(82801AA
only)
I/OD
Alert On LAN* Clock (82801AA only):
External pull-up is required
NOTES:
1. This signal requires a pull-up resistor, even if it is not used.
2. GPIO[27] is a non-muliplexed signal on the ICH0 (82801AB).
ALERTDATA
GPIO[28]
(82801AA
only)
I/OD
Alert On LAN* Data (82801AA only):
External pull-up is required
NOTES:
1. This signal requires a pull-up resistor, even if it is not used.
2. GPIO[28] is a non-muliplexed signal on the ICH0 (82801AB).
Table 2-12. Real Time Clock Interface
Name
Type
Description
RTCX1
Special
Crystal Input 1:
Connected to the 32.768 KHz crystal. If no external crystal is used,
then RTCX1 can be driven with the desired clock rate.
RTCX2
Special
Crystal Input 2:
Connected to the 32.768 KHz crystal. If no external crystal is used,
then RTCX2 should be left floating.
VBIAS
I
RTC Bias Voltage:
This pin is used to provide a reference voltage. The DC voltage
applied to this pin sets a current which is mirrored throughout the oscillator and
buffer circuitry.