82801FB Datasheet, PDF (417/786 Pages) Intel Corporation – Intel I/O Controller Hub 6 (ICH6) Family

LPC Interface Bridge Registers (D31:F0)
Bit
Description
SLP_SMI_EN — R/W.
0 = Disables the generation of SMI# on SLP_EN. Note that this bit must be 0 before the software
4
attempts to transition the system into a sleep state by writing a 1 to the SLP_EN bit.
1 = A write of 1 to the SLP_EN bit (bit 13 in PM1_CNT register) will generate an SMI#, and the
system will not transition to the sleep state based on that write to the SLP_EN bit.
LEGACY_USB_EN — R/W.
3
0 = Disable.
1 = Enables legacy USB circuit to cause SMI#.
BIOS_EN — R/W.
0 = Disable.
2
1 = Enables the generation of SMI# when ACPI software writes a 1 to the GBL_RLS bit
(D31:F0:PMBase + 04h:bit 2). Note that if the BIOS_STS bit (D31:F0:PMBase + 34h:bit 2),
which gets set when software writes 1 to GBL_RLS bit, is already a 1 at the time that BIOS_EN
becomes 1, an SMI# will be generated when BIOS_EN gets set.
End of SMI (EOS) — R/W (special). This bit controls the arbitration of the SMI signal to the
processor. This bit must be set for the ICH6 to assert SMI# low to the processor after SMI# has
been asserted previously.
0 = Once the ICH6 asserts SMI# low, the EOS bit is automatically cleared.
1 = When this bit is set to 1, SMI# signal will be de-asserted for 4 PCI clocks before its assertion. In
1
the SMI handler, the processor should clear all pending SMIs (by servicing them and then
clearing their respective status bits), set the EOS bit, and exit SMM. This will allow the SMI
arbiter to re-assert SMI upon detection of an SMI event and the setting of a SMI status bit.
NOTE: ICH6 is able to generate 1st SMI after reset even though EOS bit is not set. Subsequent
SMI require EOS bit is set.
GBL_SMI_EN — R/W.
0 = No SMI# will be generated by ICH6. This bit is reset by a PCI reset event.
0
1 = Enables the generation of SMI# in the system upon any enabled SMI event.
NOTE: When the SMI_LOCK bit is set, this bit cannot be changed.
Intel^® I/O Controller Hub 6 (ICH6) Family Datasheet
417