Datasheet

Host-Primary PCI Express* Bridge Registers (D1:F0)
156 Datasheet
6.12 IOBASE1—I/O Base Address
B/D/F/Type: 0/1/0/PCI
Address Offset: 1Ch
Default Value: F0h
Access: RO, RW
Size: 8 bits
This register controls the processor to PCI Express I/O access routing based on the
following formula:
IO_BASE ≤ address ≤ IO_LIMIT
Only upper 4 bits are programmable. For the purpose of address decode address bits
A[11:0] are treated as 0. Thus the bottom of the defined I/O address range will be
aligned to a 4 KB boundary.
6.13 IOLIMIT1—I/O Limit Address
B/D/F/Type: 0/1/0/PCI
Address Offset: 1Dh
Default Value: 00h
Access: RW, RO
Size: 8 bits
This register controls the processor to PCI Express I/O access routing based on the
following formula:
IO_BASE ≤ address ≤ IO_LIMIT
Only upper 4 bits are programmable. For the purpose of address decode, address bits
A[11:0] are assumed to be FFFh. Thus, the top of the defined I/O address range will be
at the top of a 4 KB aligned address block.
Bit Access
Default
Value
Description
7:4 RW Fh
I/O Address Base (IOBASE): Corresponds to A[15:12] of the I/O addresses
passed by bridge 1 to PCI Express.
3:0 RO 0h Reserved
Bit Access
Default
Value
Description
7:4 RW 0h
I/O Address Limit (IOLIMIT): Corresponds to A[15:12] of the I/O address
limit of device #1. Devices between this upper limit and IOBASE1 will be passed
to the PCI Express hierarchy associated with this device.
3:0 RO 0h Reserved