I/O Write Operation - 1.0 English

Versal Adaptive SoC Integrated Block for PCI Express LogiCORE IP Product Guide (PG343)

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1.0 English

The transfer of an I/O write request on the completer request interface is similar to that of a memory write request with a one-Dword payload. The transfer starts with the 128-bit descriptor, followed by the one-Dword payload. When the Dword-aligned mode is in use, the payload Dword immediately follows the descriptor. When the 128-bit address aligned mode is in use, the payload Dword is supplied in bits 255:128, and its alignment is based on the address in the descriptor. The First Byte Enable bits in the m_axis_cq_tuser indicate the valid bytes in the payload. The byte enable bits byte_en also provide this information.

Because an I/O write is a Non-Posted transaction, the user logic must respond to it with a Completion containing no data payload. The Completions for I/O requests are be sent in any order. Errors associated with the I/O write transaction can be signaled to the requester by setting the Completion Status field in the completion descriptor to CA (Completer Abort) or UR (Unsupported Request), as is appropriate. The operation of the completer completion interface is described in 64/128/256-bit Completer Interface and 512-bit Completer Interface.