This section describes the operation of the completer interface in the user-side interfaces associated with the 512-bit AXI4-Stream Interface. The following figure illustrates the connections between the soft bridge, PCIe® core and user application. The soft bridge converts the 256-bit packets at 500 MHz into 512-bit packets at 250 MHz.
The completer interface maps the transactions (memory, I/O read/write, messages, Atomic Operations) received from the PCIe link into transactions on the completer request interface based on the AXI4-Stream protocol. The completer interface is required to be connected to the user application in all PCIe Endpoint implementations, but is optional for Root Complexes. The completer interface consists of two separate interfaces, one for data transfer in each direction. Each interface is based on the AXI4-Stream protocol, with a data width of 512 bits. The completer request interface is for transfer of requests (with any associated payload data) to the user application, and the completer completion interface is for receiving the Completion data (for a Non-Posted request) from the user application for forwarding on the link. The two interfaces operate independently. That is, the core can transfer new requests over the completer request interface while receiving a Completion for a previous request.