
82801AA and 82801AB ICH Datasheet
7-7
Hub Interface-to-PCI Bridge Registers (D30:F0)
7.1.13
SMLT—Secondary Master Latency Timer Register
(HUB-PCI—D30:F0)
Offset Address:
Default Value:
1Bh
00h
Attribute:
Size:
R/W
8 bits
This Master Latency Timer (MLT) controls the amount of time that the ICH will continue to burst
data as a master on the PCI bus. When the ICH starts the cycle after being granted the bus, the
counter is loaded and starts counting down from the assertion of FRAME#. If the internal grant to
this device is removed, then the expiration of the MLT counter will result in the deassertion of
FRAME#. If the internal grant has not been removed, then the ICH can continue to own the bus.
7.1.14
IOBASE—I/O Base Register (HUB-PCI—D30:F0)
Offset Address:
Default Value:
1Ch
F0h
Attribute:
Size:
R/W
8 bits
7.1.15
IOLIM—I/O Limit Register (HUB-PCI—D30:F0)
Offset Address:
Default Value:
1Dh
00h
Attribute:
Size:
R/W
8 bits
Bit
Description
7:3
Master Latency Count.
5-bit value that indicates the number of PCI clocks, in 8-clock increments,
that the ICH will remain as master of the bus.
2:0
Reserved.
Bit
Description
7:4
I/O Address Base bits [15:12]—R/W.
I/O Base bits corresponding to address lines 15:12 for 4 KB
alignment. Bits 11:0 are assumed to be padded to 000h.
3:0
I/O Addressing Capability—RO.
This is hardwired to 0h, indicating that the hub interface to PCI
bridge does not support 32-bit I/O addressing. This means that the I/O base & limit upper address
registers must be read only.
Bit
Description
7:4
I/O Address Limit bits [15:12]—R/W.
I/O Base bits corresponding to address lines 15:12 for 4 KB
alignment. Bits 11:0 are assumed to be padded to FFFh.
3:0
I/O Addressing Capability—RO.
This is hardwired to 0h, indicating that the hub interface to PCI
bridge does not support 32-bit I/O addressing. This means that the I/O base & limit upper address
registers must be read only.