8.4.4. TCM arbitration

Each TCM port receives requests from the LSU, PFU, and AXI slave. In most cases, the LSU has the highest priority, followed by the PFU, with the AXI slave having lowest priority.

When a higher-priority device is accessing a TCM port, an access from a lower-priority device must stall.

When either the LSU or the AXI slave interface is performing a read-modify-write operation on a TCM port, various internal data hazards exist for either the AXI-slave interface or the LSU. In these cases, additional stall cycles are generated, beyond those normally required for arbitration. For optimum performance of the processor when configured with ECC, ensure that all write bursts to the TCM from the AXI slave interface write an entire data chunk, that is, 32-bits or 64-bits, naturally aligned, depending on the error scheme.

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