82801DB Datasheet, PDF (296/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

LPC Interface Bridge Registers (D31:F0)
9.1.10
9.1.11
PMBASE—ACPI Base Address (LPC I/F—D31:F0)
Offset Address:
Default Value:
Lockable:
40–43h
00000001h
No
Attribute:
Size:
Usage:
Power Well:
R/W, RO
32 bit
ACPI, Legacy
Core
Sets base address for ACPI I/O registers, GPIO registers and TCO I/O registers. Can be mapped
anywhere in the 64K I/O space on 128-byte boundaries.
Bit
31:16
15:7
6:1
0
Description
Reserved
Base Address — R/W. Provides 128 bytes of I/O space for ACPI, GPIO, and TCO logic. This is
placed on a 128-byte boundary.
Reserved
Resource Indicator — RO. Tied to 1 to indicate I/O space.
ACPI_CNTL—ACPI Control (LPC I/F — D31:F0)
Offset Address: 44h
Default Value: 00h
Lockable:
No
Attribute:
Size:
Usage:
Power Well:
R/W
8 bit
ACPI, Legacy
Core
Bit
Description
7:5 Reserved
ACPI Enable (ACPI_EN) — R/W.
0 = Disable.
4 _{1 = Decode of the I/O range pointed to by the ACPI Base register is enabled, and the ACPI power}
management function is enabled. Note that the APM power management ranges (B2/B3h) are
always enabled and are not affected by this bit.
3 Reserved
SCI IRQ Select (SCI_IRQ_SEL) — R/W. This field specifies on which IRQ the SCI will internally
appear. If not using the APIC, the SCI must be routed to IRQ9-11, and that interrupt is not sharable
with the SERIRQ stream, but is shareable with other PCI interrupts. If using the APIC, the SCI can
also be mapped to IRQ20-23, and can be shared with other interrupts.
000 = IRQ9
001 = IRQ10
010 = IRQ11
2:0 ^{011 = Reserved}
100 = IRQ20 (Only available if APIC enabled)
101 = IRQ21 (Only available if APIC enabled)
110 = IRQ22 (Only available if APIC enabled)
111 = IRQ23 (Only available if APIC enabled)
NOTE: When the TCO interrupt is mapped to APIC interrupts 9, 10 or 11, the signal is in fact active
high. When the TCO interrupt is mapped to IRQ 20, 21, 22, or 23 the signal is active low and
can be shared with PCI interrupts that may be mapped to those same signals (IRQs).
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Intel^® 82801DB ICH4 Datasheet