Configuration Management Interface - 4.4 English

The ports used by configuration registers are described in Table: Configuration Status Interface Port Descriptions . Root Ports must use the Configuration Port to set up the Configuration Space. Endpoints can also use the Configuration Port to read and write; however, care must be taken to avoid adverse system side effects.

The user application must supply the address as a Dword address, not a byte address.

TIP: To calculate the Dword address for a register, divide the byte address by four.

For example:

For the Command/Status register in the PCI Configuration Space Header:

• The Dword address of is 01h .

Note: The byte address is 04h .

For BAR0:

• The Dword address is 04h .

Note: The byte address is 10h .

To read any register in configuration space, the user application drives the register Dword address onto cfg_mgmt_addr[9:0] . cfg_mgmt_addr[17:10] selects the PCI Function associated with the configuration register. The core drives the content of the addressed register onto cfg_mgmt_read_data[31:0] . The value on cfg_mgmt_read_data[31:0] is qualified by signal assertion on cfg_mgmt_read_write_done . This Figure illustrates an example with read from the Configuration Space.

To write any register in configuration space, the user logic places the address on cfg_mgmt_addr bus , write data on cfg_mgmt_write_data , byte-valid on cfg_mgmt_byte_enable [3:0] , and asserts the cfg_mgmt_write signal. In response, the core asserts the cfg_mgmt_read_write_done signal when the write is complete (which can take several cycles). The user logic must keep cfg_mgmt_addr , cfg_mgmt_write_data , cfg_mgmt_byte_enable and c fg_mgmt_write stable until cfg_mgmt_read_write_done is asserted. The user logic must also deassert cfg_mgmt_write in the cycle following the cfg_mgmt_read_write_done from the core.

When the core is configured in the Root Port mode, when you assert cfg_mgmt_type1_cfg_reg_access input during a write to a Type-1 PCI™ Configuration register forces a write into certain read-only fields of the register.