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AXI Bridge for PCI Express v2.4
59
PG055 June 4, 2014
Chapter 3:
Designing with the Core
Illegal Burst Type
The Slave Bridge monitors AXI read and write burst type inputs to ensure that only the INCR
(incrementing burst) type is requested. Any other value on these inputs is treated as an
error condition and the Slave Illegal Burst (SIB) interrupt is asserted. In the case of a read
request, the Bridge asserts SLVERR for all data beats and arbitrary data is placed on the
s_axi_rdata
bus. In the case of a write request, the Bridge asserts SLVERR for the write
response and all write data is discarded.
Completion TLP Errors
Any request to the bus for PCIe (except for posted Memory write) requires a completion TLP
to complete the associated AXI request. The Slave side of the Bridge checks the received
completion TLPs for errors and checks for completion TLPs that are never returned
(Completion Timeout). Each of the completion TLP error types are discussed in the
subsequent sections.
Unexpected Completion
When the Slave Bridge receives a completion TLP, it matches the header RequesterID and
Tag to the outstanding RequesterID and Tag. A match failure indicates the TLP is an
Unexpected Completion which results in the completion TLP being discarded and a Slave
Unexpected Completion (SUC) interrupt strobe being asserted. Normal operation then
continues.
Unsupported Request
A device for PCIe might not be capable of satisfying a specific read request. For example,
the read request targets an unsupported address for PCIe causing the completer to return
a completion TLP with a completion status of 0b001 - Unsupported Request. The completer
can also return a completion TLP with a completion status that is reserved according to the
2.1 PCIe Specification, which must be treated as an unsupported request status. When the
slave bridge receives an unsupported request response, the Slave Unsupported Request
(SUR) interrupt is asserted and the SLVERR response is asserted with arbitrary data on the
memory mapped AXI4 bus.
Completion Timeout
A Completion Timeout occurs when a completion (Cpl) or completion with data (CplD) TLP
is not returned after an AXI to PCIe read request. Completions must complete within the
C_COMP_TIMEOUT parameter selected value from the time the MemRd for PCIe request is
issued. When a completion timeout occurs, a Slave Completion Timeout (SCT) interrupt is
asserted and the SLVERR response is asserted with arbitrary data on the memory mapped
AXI4 bus.