2.7.6. Invariant-timing packets and overflow

If a write is performed to an invariant-timing stimulus port location on the software stimulus interface, the write appears to be immediately accepted, regardless of the state of the STM buffers. If there is not enough space for the generated packet on the STM buffer, the data is discarded and does not appear in the trace output.

If data is discarded as a result of invariant timing writes made while the STM buffer is full, a MERR packet is added to the STM buffer when space next becomes available on the buffer. Only one MERR packet is generated regardless of the number of discarded transactions, until:

If new data is discarded with a master ID different to the previously discarded transaction, and there is an MERR pending that has not been accepted by the STM FIFO, a GERR packet is generated instead.

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