
IBM21P100BGC
IBM 133 PCI-X Bridge R2.0
ppb20_pcix_regs.fm.01
October 15, 2001
Configuration Registers
5.2.4.16 Secondary Latency Timer Register
This register specifies, in PCI bus clock units, the value of the secondary latency timer for this device as a bus
master. Bus masters that can burst for more than two data phases must implement this register as Read/
Write.
5.2.4.17 I/O Base Register
The I/O Base register specifies the base of the I/O address range bits 15:12 and is used in conjunction with
the I/O limit register and I/O base upper 16 bits and I/O limit upper 16 bits registers to specify a range of 32-
bit addresses supported for I/O transactions on the PCI bus. Address bits 11:0 are assumed to be x‘000’ for
the base address. This register also specifies that the bridge supports 32-bit I/O addressing.
Address Offset
x‘1B’
Access
See individual fields
Reset Value
x'00' in the PCI mode, x'40' in the PCI-X mode
Secondary Latency Timer
7
6
5
4
3
2
1
0
Bit(s)
Access
FieldNameand Description
7:3
RW
Read/Write to set granularity in 8-cycle increments.
2:0
RO
Forced to b‘000’ to force 8-cycle increments for the latency timer.
Address Offset
x‘1C’
Access
See individual fields
Reset Value
x‘X1’
I/O Base
Address
32-Bit
Addressing
7
6
5
4
3
2
1
0
Bit(s)
Access
Field Name and Description
7:4
RW
I/O Base Address
Address bits 15:12 of the base address for the address range of I/O operations that are passed from the primary
to the secondary PCI bus.
3:0
RO
Set to b‘0001’ to indicate that 32-bit I/O addressing is supported.