Register Description
R
Bit | Descriptions |
|
|
31 | Configuration Enable (CFGE). |
| 0 = Disable. |
| 1 = Enable. Accesses to PCI configuration space are enabled. |
|
|
30:24 | Reserved. These bits are read only and have a value of 0. |
|
|
23:16 | Bus Number. When Bus Number is programmed to 00h, the target of the configuration cycle is |
| a hub interface agent (MCH, ICH2, etc.). |
| The configuration cycle is forwarded to the hub interface, if Bus Number is programmed to 00h |
| and the MCH is not the target (the device number is ≥ 2). |
| If Bus Number is |
| Register of device 1, a Type 0 PCI configuration cycle will be generated on AGP. |
| If Bus Number is |
| device 1 and less than or equal to the value programmed into the Subordinate Bus Number |
| register of device 1 a Type 1 PCI configuration cycle will be generated on AGP. |
| If Bus Number is |
| Secondary Bus Number or Subordinate Bus Number register, then a hub interface Type 1 |
| configuration cycle is generated. |
|
|
15:11 | Device Number. This field selects one agent on the PCI bus selected by the Bus Number field. |
| When the Bus Number field is 00, the MCH decodes the Device Number field. The MCH is |
| always Device Number 0 for the |
| |
| devices are selected. |
| If the Bus Number is |
| Number register a Type 0 PCI configuration cycle is generated on AGP. The MCH decodes the |
| Device Number field ([15:11]) and assert the appropriate GAD signal as an IDSEL. For |
| PCI Bridge translation, one of the 16 IDSELs is generated. When bit [15] = 0, bits [14:11] are |
| decoded to assert a signal AD[31:16] IDSEL. GAD16 is asserted to access Device 0, GAD17 for |
| Device 1, and so forth up to Device 15 which asserts AD31. All device numbers higher than 15 |
| cause a type 0 configuration access with no IDSEL asserted, which results in a Master Abort |
| reported in the MCH’s “virtual” |
| For Bus Numbers resulting in hub interface configuration cycles, the MCH propagates the device |
| number field as A[15:11]. For bus numbers resulting in AGP type 1 configuration cycles, the |
| device number is propagated as GAD[15:11]. |
|
|
10:8 | Function Number. This field is mapped to GAD[10:8] during AGP configuration cycles and |
| A[10:8] during Hub Interface configuration cycles. This allows the configuration registers of a |
| particular function in a |
| 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 |
| GAD[7:2] during AGP configuration cycles and A[7:2] during hub interface configuration cycles. |
|
|
1:0 | Reserved. |
|
|
Intel® 82845 MCH for SDR Datasheet | 35 |