
IBM21P100BGB
IBM 133 PCI-X Bridge R1.1
ppb11_operations.fm.03
July 9, 2001
Bus Operation
Page 21 of 131
The register number is found in both Type 0 and Type 1 formats and gives the DWord address of the config-
uration register to be accessed. The function number is also included in both formats and indicates which
function of a multi-function device is to be accessed. For single-function devices, this value is not decoded.
Configuration transaction addresses for Type 1 and PCI-X Type 0 formats also include a 5-bit field desig-
nating the device number that identifies the device on the target PCI bus that is to be accessed. This device
number is decoded to determine which IDSEL is asserted for the transaction. Finally, Type 1 transactions
also include a bus number field that is used by the bridge to determine where in the bus hierarchy the trans-
action is targeted.
3.4.1 Configuration Type 0 Access to Bridge
The configuration space of the bridge is accessed by a Type 0 configuration transaction issued on the
primary interface. The configuration space of the bridge cannot be accessed from the secondary bus. The
bridge responds to a Type 0 configuration transaction by accepting the transaction when the following condi-
tions are met during the address phase:
The command on P_C/BE(3:0)# indicates a configuration read or configuration write transaction;
P_AD(1:0) are b‘00’;and
P_IDSEL is asserted.
Figure 2: Configuration Transaction Address Formats
31
0
2
7
8
11 10
Reserved
Function
Register Number
0
1
PCI Type 1
Device Number
Bus Number
15
16
23
24
Number
AD(31:0)
31
0
2
7
8
11 10
Function
Register Number
0
1
PCI Type 0
See PCI 2.2 Specification and table below
Number
AD(31:0)
31
0
2
7
8
11 10
Reserved
Function
Register Number
0
1
PCI-X Type 1
Device Number
Bus Number
15
16
23
24
Number
AD(31:0)
31
0
2
7
8
11 10
Function
Register Number
0
1
PCI-X Type 0
See PCI-X Addendum and table below
Number
AD(31:0)
16 15
Device Number