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5. Configuration Transactions > PCIe Enhanced Configuration Mechanism
46
PEB383 User Manual
July 25, 2011
Integrated Device Technology, Inc.
Confidential - NDA Required
To translate the forwarded transaction from a PCIe Type 1 configuration request to a PCI Type 1
configuration transaction, the PEB383 does the following:
•
Sets address bits PCI_AD[1:0] as 0b01
•
PCI Register Number, Function Number, Device Number, and Bus Number (address bits
PCI_AD[23:2]) are generated directly – that is, unmodified – from the PCIe configuration
transaction’s Register Address, Function Number, Device Number, and Bus Number fields,
respectively.
•
Checks 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 generates
PCI_AD[27:24] as 0b0000.
5.2.5
Type 1 to Special Cycle Forwarding
When the PEB383 receives a PCIe Type 1 configuration write request transaction, it converts it to a
Special Cycle on its PCI Interface when the following conditions are met by the transaction:
•
The Bus Number field matches the Secondary Bus Number register value
•
The Device Number field is all ones (equals 0b1_1111)
•
The Function Number field is all ones (equals 0b111)
•
The Register Address and Extended Register Address are both all zeros (equal 0b00_0000 and
0b0000, respectively).
5.3
PCIe Enhanced Configuration Mechanism
The PCIe Enhanced Configuration Mechanism adds four additional bits to the Register Address
field,
thereby expanding the space to 4096 bytes. The PEB383 forwards configuration transactions only
when the Extended Register Address
bits are all zero. This prevents address aliasing on the PCI bus
that does not support Extended Register Addressing. If a configuration transaction targets the PCI bus
and has a non-zero value in the Extended Register Address
field, the PEB383 handles the transaction as
if it received a Master-Abort on the PCI bus and then does the following:
•
Sets the appropriate status bits for the destination bus, as if the transaction had executed and
resulted in a Master-Abort
•
Generates a PCIe completion with Unsupported Request status