
IBM21P100BGC
IBM 133 PCI-X Bridge R2.0
Configuration Registers
ppb20_pcix_regs.fm.01
October 15, 2001
6
RW
Secondary Bus Reset
0
Do not force the assertion of the secondary interface signal RST#.
1
Force the assertion of the secondary interface signal RST#.
5
RW
Master-Abort Mode
0
Do not report master-aborts, return x‘FFFF FFFF’ on reads and discard data on writes.
1
Report master-aborts by signaling target-abort if possible or by assertion of SERR# (if enabled).
If in thePCI-X mode thebridgewill returna split completion messageand it is up to thehost bridgetoreturn
x‘FFFF FFFF’ on any non-posted transaction when the non-posted transaction ends in a master abort.
4
RO
Reserved
0
Must return 0.
3
RW
VGA Enable
0
Do not forward VGA compatible memory and I/O addresses from the primary to the secondary inter-
face unless they are enabled for forwarding by the defined I/O and memory address ranges.
1
Forward VGA compatible memory and I/O addresses from the primary interface to the secondary
interface (if the I/O Enable and Memory Enable bits are set) independent of the I/O and memory
address ranges and independent of the ISA Enable bit.
2
RW
ISA Enable
0
Forward downstream all I/O addresses in address range defined by I/O Base and I/O Limit registers.
1
Forward upstream ISA I/O addresses in address range defined by I/O Base and I/O Limit registers in
the first 64 KB of PCI I/O address space (top 768 bytes of each 1 KB block).
1
RW
SERR# Enable
0
Disable the forwarding of secondary SERR# to primary SERR#.
1
Enable the forwarding of secondary SERR# to primary SERR#.
0
RW
Parity Error Response Enable
0
Ignore address and data parity errors on the secondary interface.
1
Enable parity error detection and reporting on the secondary interface.
Controls the response to address and data parity errors on the secondary interface. If this bit is set, the bridge
must take its normal action when a parity error is detected. If this bit is cleared, the bridge must ignore any par-
ity errors that it detects and continue normal operation. In either case, the parity error detected bit of the sec-
ondary status register gets set if an address or data parity error is detected.
Bit(s)
Access
Field Name and Description