82801BA Datasheet, PDF (159/498 Pages) Intel Corporation – Intel 82801BA I/O Controller Hub 2 (ICH2) and Intel 82801BAM I/O Controller Hub 2 Mobile

Functional Description
If a boot is unsuccessful (processor does not fetch the first instruction), then the ICH2 will send an
Alert on LAN* message with the processor event status bit set and the next incremented sequence
number. This message will be sent as soon as the lockup is detected (2 TCO timer time-outs).
If the system is in a G1 (S1–S4) state the ICH2 will send a heartbeat message every 30–32 seconds.
If an event occurs prior to the system being shutdown, the ICH2 immediately sends an event
message with the next incremented sequence number. After the event message, the ICH2 resumes
sending heartbeat messages.
Note:
Normally, the ICH2 does not send heartbeat messages while in the G0 state (except in the case of a
lockup). However, if a hardware event (or heartbeat) occurs just as the system is transitioning into
a G0 state, the hardware continues to send the message even though the system is in a G0 state (and
the status bits may indicate this).
When used with an external Alert on LAN* enabled LAN controller, the ICH2 sends these
messages via the SMLINK signals. When sending messages via these signals, the ICH2 abides by
the SMBus rules associated with collision detection. It delays starting a message until the bus is
idle and detects collisions. If a collision is detected, the ICH2 waits until the bus is idle and tries
again. Table 5-52 shows the data included in the Alert on LAN* messages.
Table 5-52. Alert on LAN* Message Data
Field
Comment
Cover Tamper Status
1 = This bit will be set if the intruder detect bit is set (INTRD_DET).
Temp Event Status
1 = This bit will be set if the ICH2THERM# input signal is asserted.
Processor Missing Event
Status
1 = This bit will be set if the processor failed to fetch the first instruction.
TCO Timer Event Status
1 = This bit is set when the TCO timer expires.
Software Event Status
1 = This bit is set when software writes a 1 to the SEND_NOW bit.
Unprogrammed FWH Event 1 = First BIOS fetch returned a value of FFh, indicating that the FWH has not
Status
yet been programmed (still erased).
GPIO Status
1 = This bit is set when GPIO[11] signal is high.
0 = This bit is cleared when GPIO[11] signal is low.
SEQ[3:0]
This is a sequence number. It will initially be 0, and will increment each time the
ICH2 sends a new message. Upon reaching 1111, then the sequence number
will roll over to 0000. MSB (SEQ3) sent first.
System Power State
00 = G0, 01 = G1, 10 = G2, 11 = Pre-Boot. MSB sent first
MESSAGE1
Same as the MESSAGE1 Register. MSB sent first.
MESSAGE2
Same as the MESSAGE2 Register. MSB sent first.
WDSTATUS
Same as the WDSTATUS Register. MSB sent first.
82801BA ICH2 and 82801BAM ICH2-M Datasheet
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