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27 Soft Power Management Registers
PM1_STS Power Management 1 Status Register
I/O Address 6000h
(ACPI PM1a_EVT_BLK) Attribute R/WC
Default Value 0000h
Size 16-bit
Lockable No
Usage ACPI or Legacy
Power Well Bits 0–7: Core,
Bits 8–15: Resume
Except Bit 11 in RTC
If bit 10 or 8 in this register is 1 and the corresponding _EN bit is set in the PM1_EN register, ICH2
generates a Wake Event. Once back in an S0 state (or if already in S0 state when the event occurs), ICH2
also generates an SCI if the SCI_EN bit is set or an SMI# if the SCI_EN bit is not set.
Note: Bit 5 does not cause an SMI# or a wake event. Bit 0 does not cause a wake event but can cause an
SMI# or SCI.
Bit Description
15 Wake Status (WAK_STS)—R/WC. This bit is not affected by hard resets caused by a CF9 write but is reset by RSMRST#.
0 = Software clears this bit by writing a 1 to the bit position.
1 = Set by hardware when the system is in one of the sleep states (via the SLP_EN bit) and an enabled wake event occurs.
Upon setting this bit, the ICH2 will transition the system to the ON state.
If the AFTERG3_EN bit is not set and a power failure occurs without the SLP_EN bit set, the system will return to an S0 state
when power returns, and the WAK_STS bit will not be set. For the 82801BAM ICH2-M, power failure could result from removing
the batteries.
If the AFTERG3_EN bit is set and a power failure occurs without the SLP_EN bit having been set, the system will go into an S5
state when power returns and a subsequent wake event will cause the WAK_STS bit to be set. Note that any subsequent wake
event would have to be caused by either a Power Button press or an enabled wake event that was preserved through the power
failure (enable bit in the RTC well).
14:12 Reserved
11 Power Button Override Status (PRBTNOR_STS)—R/WC. This bit is not affected by hard resets caused by a CF9 write and is
not reset by RSMRST#. Thus, this bit will be preserved through a power failure.
0 = The BIOS or SCI handler can clear this bit by writing a 1 to it.
1 = Set by hardware anytime a Power Button Override Event occurs which occurs when the power button is pressed for at least
4 consecutive seconds. The power button override causes an unconditional transition to the S5 state and sets the AFTERG3 bit.
This bit can also be set by the SMBus Slave logic.
10 RTC Status (RTC_STS)—R/WC. This bit is not affected by hard resets caused by a CF9 write but is reset by RSMRST#.
0 = Software clears this bit by writing a 1 to the bit position.
1 = Set by hardware when the RTC generates an alarm (assertion of the IRQ8# signal). Additionally if the RTC_EN bit is set, the
setting of the RTC_STS bit will generate a wake event.
9 Reserved
8 Power Button Status (PWRBTN_STS)—R/WC. This bit is not affected by hard resets caused by a
CF9 write.
1 = This bit is set by hardware when the PWRBTN# signal is asserted Low, independent of any other enable bit.
In the S0 state, while PWRBTN_EN and PWRBTN_STS are both set, an SCI (or SMI# if SCI_EN is not set) will be generated. In
any sleeping state S1–S5, while PWRBTN_EN and PWRBTN_STS are both set, a wake event is generated.
0 = If the PWRBTN# signal is held low for more than 4 seconds, the hardware clears the PWRBTN_STS bit, sets the
PWRBTNOR_STS bit, and the system transitions to the S5 state with only PWRBTN# enabled as a wake event. This bit can be
cleared by software by writing a one to the bit position.
7:6 Reserved
5 Global Status (GBL _STS)—R/WC.
1 = Set when an SCI is generated due to BIOS wanting the attention of the SCI handler. BIOS has a corresponding bit,
BIOS_RLS, which will cause an SCI and set this bit.
0 = The SCI handler should then clear this bit by writing a 1 to the bit location.
4 ICH2 (82801BA):
Reserved
3:1 Reserved
0 Timer Overflow Status (TMROF_STS)—R/WC.
1 = This bit gets set any time bit 22 of the 24-bit timer goes high (bits are numbered from 0 to 23).
This will occur every 2.3435 seconds. When the TMROF_EN bit is set, then the setting of the TMROF_STS bit will additionally
generate an SCI or SMI# (depending on the SCI_EN).
0 = The SCI or SMI# handler clears this bit by writing a 1 to the bit location.
An0065. CPU-1450 Soft Power Management
Table 10. PM1_STS Power Management 1 Status Register