307013-003 Datasheet, PDF (371/848 Pages) Intel Corporation – Intel I/O Controller Hub 7

LPC Interface Bridge Registers (D31:F0)
10.1.18 SIRQ_CNTL—Serial IRQ Control Register
(LPC I/F—D31:F0)
Offset Address: 64h
Default Value: 10h
Lockable:
No
Attribute:
Size:
Power Well:
R/W, RO
8 bit
Core
Bit
Description
Serial IRQ Enable (SIRQEN) — R/W.
7 _{0 = The buffer is input only and internally SERIRQ will be a 1.}
1 = Serial IRQs will be recognized. The SERIRQ pin will be configured as SERIRQ.
Serial IRQ Mode Select (SIRQMD) — R/W.
0 = The serial IRQ machine will be in quiet mode.
1 = The serial IRQ machine will be in continuous mode.
6
NOTE: For systems using Quiet Mode, this bit should be set to 1 (Continuous Mode) for
at least one frame after coming out of reset before switching back to Quiet
Mode. Failure to do so will result in the Intel^® ICH7 not recognizing SERIRQ
interrupts.
5:2
Serial IRQ Frame Size (SIRQSZ) — RO. Fixed field that indicates the size of the
SERIRQ frame as 21 frames.
Start Frame Pulse Width (SFPW) — R/W. This is the number of PCI clocks that the
SERIRQ pin will be driven low by the serial IRQ machine to signal a start frame. In
continuous mode, the ICH7 will drive the start frame for the number of clocks specified.
In quiet mode, the ICH7 will drive the start frame for the number of clocks specified
1:0 ^{minus one, as the first clock was driven by the peripheral.}
00 = 4 clocks
01 = 6 clocks
10 = 8 clocks
11 = Reserved
Intel ^® ICH7 Family Datasheet
371