Functional Description
5-74
Intel
82801BA ICH2 Datasheet
5.12.6.1
Initiating Sleep State
Sleep states (S1–S5) are initiated by:
Masking interrupts, turning off all bus master enable bits, setting the desired type in the
SLP_TYP field, and then setting the SLP_EN bit. The hardware will then attempt to gracefully
put the system into the corresponding Sleep state by first going to a C2 state. See
Section 5.12.5
for details on going to the C2 state.
Pressing the PWRBTN# signal for more than 4 seconds to cause a Power Button Override
event. In this case the transition to the S5 state will be less graceful, since there will be no
dependencies on observing Stop-Grant cycles from the processor or on clocks other than the
RTC clock.
5.12.6.2
Exiting Sleep States
Sleep states (S10–S5) are exited based on Wake events. The Wake events will force the system to a
full on state (S0), although some non-critical subsystems might still be shut off and have to be
brought back manually. For example, the hard disk may be shut off during a sleep state, and have to
be enabled via a GPIO pin before it can be used.
Upon exit from the ICH2-controlled Sleep states, the WAK_STS bit will be set. The possible
causes of Wake Events (and their restrictions) are shown in
Table 5-43
.
Note:
If in the S5 state due to a powerbutton override, the only wake event is power button.
Table 5-42. Sleep Types
Sleep Type
Comment
S1
ICH2 asserts the CPUSLP# signal. This lowers the processor’s power consumption. No
snooping is possible in this state.
S3
ICH2 asserts SLP_S3#. The SLP_S3# signal controls the power to non-critical circuits. Power
is only be retained to devices needed to wake from this sleeping state, as well as to the
memory.
S4
ICH2 asserts SLP_S3# and SLP_S5#. The SLP_S5# signal shuts off the power to the memory
subsystem. Only devices needed to wake from this state should be powered.
S5
Same as S4. ICH2 asserts SLP_S3# and SLP_S5#. The SLP_S5# signal shuts off the power
to the memory subsystem. Only devices needed to wake from this state should be powered.
Table 5-43. Causes of Wake Events
Cause
States Can
Wake From
How Enabled
RTC Alarm
S1
–
S5
(Note 1)
Set RTC_EN bit in PM1_EN Register
Power Button
S1
–
S5
S1
–
S5
(Note 1)
Always enabled as Wake event
GPI[0:n]
GPE1_EN register
USB
S1
–
S4
S1
–
S5
S1
–
S5
(Note 1)
Set USB1_EN and USB2_EN bits in GPE0_EN Register
LAN
Will use PME#. Wake enable set with LAN logic.
RI#
Set RI_EN bit in GPE0_EN Register
AC97
S1
–
S5
Set AC97_EN bit in GPE0_EN Register
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