
The requester completion interface supports two distinct data alignment modes for transferring
payloads, which are during core customization in the Vivado
®
IDE. In the Dword-aligned mode,
the core transfers the first Dword of the Completion payload immediately after the last Dword of
the descriptor. In the 128-bit address aligned mode, the core starts the payload transfer in the
second 128-bit quarter of the 1024-bit word, following the descriptor in the first quarter. The
first Dword of the payload can be in any of the four possible Dword positions in the second
quarter, and its offset f the is determined by address offset provided by the user logic when it
sent the request to the core (that is, the setting of the
addr_offset
input of the requester
request interface). Thus, the 128-bit address aligned mode can be used on the requester
completion interface only if the requester request interface is also configured to use the 128-bit
address aligned mode.
Requester Completion Descriptor Format
The requester completion interface of the core sends completion data received from the link to
the user application as AXI4-Stream packets. Each packet starts with a descriptor, and can have
payload data following the descriptor. The descriptor is always 12 bytes long, and is sent in the
first 12 bytes of the completion packet. When the completion data is split into multiple Split
Completions, the core sends each Split Completion as a separate AXI4-Stream packet, with its
own descriptor.
The format of the requester completion descriptor is illustrated in the following figure. The
individual fields of the requester completion descriptor are described in the following table.
Chapter 4: Designing with the Core
PG346 (v3.3) November 16, 2022
CPM Mode for PCI Express
173