Intel
82801BA ICH2 Datasheet
5-69
Functional Description
Table 5-38
shows the transitions rules among the various states. Note that transitions among the
various states may appear to temporarily transition through intermediate states. For example, in
going from S0 to S1, it may appear to pass through the G0/S0/C2 states. These intermediate
transitions and states are not listed in the table.
NOTES:
1. Some wake events can be preserved through power failure.
G1/S4
Suspend-To-Disk (STD):
The context of the system is maintained on the disk. All power is
then shut off to the system except for the logic required to resume. Externally appears same as
S5, but may have different wake events.
G2/S5
Soft Off (SOFF):
System context is not maintained. All power is shut off except for the logic
required to restart. A full boot is required when waking.
G3
Mechanical OFF (MOFF):
System context not maintained. All power is shut off except for the
RTC. No “Wake” events are possible, because the system does not have any power. This state
occurs if the user removes the batteries, turns off a mechanical switch, or if the system power
supply is at a level that is insufficient to power the “waking” logic. When system power returns,
transition depends on the state just prior to the entry to G3 and the AFTERG3 bit in the
GEN_PMCON3 register (D31:F0, offset A4). Refer to
Table 5-46
for more details.
Table 5-37. General Power States for Systems using ICH2
State/
Substates
Legacy Name / Description
Table 5-38. State Transition Rules for ICH2
Present
State
Transition Trigger
Next State
G0/S0/C0
Processor halt instruction
Level 2 Read
Level 3 Read
SLP_EN bit set
Power Button Override
Mechanical Off/Power Failure
G0/S0/C1
G0/S0/C2
G0/S0/C3
G1/Sx or G2/S5state
G2/S5
G3
G0/S0/C1
Any Enabled Break Event
STPCLK# goes active
Power Button Override
Power Failure
G0/S0/C0
G0/S0/C2
G2/S5
G3
G0/S0/C2
Any Enabled Break Event
STPCLK# goes inactive and previously
in C1
Power Button Override
Power Failure
G0/S0/C0
G0/S0/C1
G2/S5
G3
G1/S1,
G1/S3, or
G1/S4
Any Enabled Wake Event
Power Button Override
Power Failure
G0/S0/C0
G2/S5
G3
G2/S5
Any Enabled Wake Event
Power Failure
G0/S0/C0
G3
G3
Power Returns
Optional to go to S0/C0 (reboot) or G2/S5
(stay off until power button pressed or
other wake event). (See Note 1)
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