5. Configuration Transactions > Configuration Transactions
45
PEB383 User Manual
July 25, 2011
Integrated Device Technology, Inc.
Confidential - NDA Required
If a Type 1 configuration transaction is received on the PCIe Interface, the following sequence of tests
is completed on the Bus Number field to determine how the PEB383 should handle the transaction:
1.
If the Bus Number field is equal to the Secondary Bus Number value and the conditions for
converting the transaction into a Special Cycle transaction are met, the PEB383 forwards the
configuration request to its PCI Interface as a Special Cycle transaction. If the conditions are not
met, the PEB383 forwards the configuration request to the PCI Interface as a Type 0 configuration
transaction.
2.
If the Bus Number field is not equal to the Secondary Bus Number value but is in the range of the
Secondary Bus Number and the Subordinate Bus Number (inclusive) values, the Type 1
configuration request is specifying a Bus Number that is located behind the bridge. In this case, the
PEB383 forwards the configuration request to the PCI Interface as a Type 1 configuration
transaction.
3.
If the Bus Number field does not satisfy the tests 1 and 2, the Type 1 configuration request
indicates a Bus Number that is not located behind the bridge. In this case, the configuration request
in invalid and PEB383 handles this as an Unsupported Request.
5.2.3
Type 1 to Type 0 Conversion
If a PCIe Type 1 configuration transaction’s Bus Number field is equal to the Secondary Bus Number
value, and the conditions for conversion to a Special Cycle transaction are not met, the PEB383
forwards the transaction to the PCI bus as a Type 0 configuration transaction. In this case, a device
connected to the PCI Interface of the bridge is the target of the Type 0 configuration transaction.
To translate and convert a PCIe Type 1 configuration transaction to a PCI Type 0 configuration
transaction, the PEB383 does the following:
•
Sets address bits PCI_AD[1:0] as 0b00
•
Sets address bits PCI_AD[7:2] the same as the PCIe transaction’s Register Address field
•
Sets address bits PCI_AD[10:8] the same as PCIe transaction’s Function Number field
•
For a Secondary bus operating in PCI mode, it drives value 0b0000 on address PCI_AD[15:11]
•
For a Secondary bus operating in PCI, the PEB383 check’s if the received Extended Register
Address field is zero. If this field is non-zero, the PEB383 does not forward the transaction and
treats it as an Unsupported Request on PCIe and a received Master-Abort on the destination bus. If
the field is zero, the PEB383 decodes the PCIe Device Number field and asserts a single address bit
in the range PCI_AD[31:16] during the address phase (for device numbers in the range 0b0_0000
to 0b0_ 1111b).
5.2.4
Type 1 to Type 1 Forwarding
If a PCIe Type 1 configuration transaction is received and the value specified by the Bus Number field
is within the range of bus numbers between the Secondary Bus Number (exclusive) and the
Subordinate Bus Number (inclusive), the PEB383 forwards the transaction to its PCI Interface as a
Type 1 configuration transaction. In this case, the target of the transaction does not reside on the PCI
Interface but is located on a bus segment further downstream.