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IBM21P100BGC
IBM 133 PCI-X Bridge R2.0
ppb20_operations.fm.01
October 15, 2001
Bus Operation
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 signal is asserted for the transaction. Finally, Type 1 transac-
tions also include a bus number field that is used by the bridge to determine where in the bus hierarchy the
transaction is targeted.
3.4.1 Configuration Type 0 Access to Bridge
The configuration space of the bridge is accessed by Type 0 configuration transactions. The configuration
space of the bridge can be accessed from either the primary bus or the secondary bus. Applications which do
not require access from the secondary bus should tie down the S_IDSEL pin.
On the primary bus, the bridge responds to a Type 0 configuration transaction by accepting the transaction
when the following conditions 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';
P_IDSEL is asserted; and
Figure 3-1. 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