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A.1.3. Bursting Slave (BAS)
The AXI-MM Bursting Slave module translates AXI-MM Read and Write transactions from the user logic to PCI Express Mrd and Mwr TLPs. The returned PCI Express CplD packets are translated to AXI-MM Read Data channel as a response to the AXI-MM read request transaction.
The BAS supports both 128-bit and 256-bit data widths to achieve the bandwidths required for Gen3 x4 and Gen4 x4. It supports bursts of up to 512 bytes and up to 64 outstanding read requests.
Completion Reordering
The AXI-MM BAS interface is a subordinate interface to the User AXI-MM interface. The User AXI-MM can initiate AXI-MM reads to the host interface and this translates to BAS Non-Posted (NP) packet interface signals. The BAS module keeps track of the initiated NP requests and tracks against the completions received from the PCIe on the scheduler completion packet interface.
Since the completion from the PCIe can come out of order, the completion reordering module ensures the returned completions are reordered against the pending requests and sent in the same order on the AXI-MM interface.