Datasheet

Datasheet 69

Bit Description

31 Configuration Enable (CFGE): When this bit is set to 1, accesses to PCI Configuration

Space are enabled. If this bit is Reset to 0, accesses to PCI Configuration Space are

disabled.

30:24 Reserved

23:16 Bus Number: When the Bus Number is programmed to 00h, the target of the

Configuration Cycle is a hub interface agent (GMCH, ICH4-M, etc.).

The Configuration Cycle is forwarded to hub interface if the Bus Number is programmed

to 00h and the GMCH/MCH is not the target (the device number is >= 2).

15:11 Device Number: This field selects one agent on the PCI Bus selected by the Bus

Number. When the Bus Number field is 00 the GMCH/MCH decode the Device Number

field. The GMCH/MCH is always Device #0 for the Host-hub interface bridge entity.

Therefore, when the Bus Number =0 and the Device Number=0-1 the internal

GMCH/MCH devices are selected.

For Bus Numbers resulting in Hub Interface Configuration cycles, the GMCH/MCH

propagates the device number field as A[15:11].

10:8 Function Number: This field is mapped to A[10:8] during Hub Interface Configuration

cycles. This allows the configuration registers of a particular function in a multi-function

device to be accessed. The GMCH/MCH ignore Configuration cycles to its internal

Devices if the function number is not equal to 0.

7:2 Register Number: This field selects one register within a particular Bus, Device, and

Function as specified by the other fields in the Configuration Address register. This field

is mapped to A[7:2] during Hub Interface Configuration cycles.

1:0 Reserved