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Can HTRANS change from IDLE to NONSEQ during AHB error response?

We know that HTRANS can change from NONSEQ to IDLE during the 2-cycle error response.

We also know that if HTRANS is NONSEQ, it can remain at NONSEQ.

But can HTRANS change from IDLE to NONSEQ?

  • Yes.

    This can happen if the transfer source is ignoring the ERROR response and is just treating it as a wait state. Then the protocol allows HTRANS to change from IDLE to NONSEQ during a waited transfer (see section 3.6.1).

    But if HTRANS is NONSEQ or SEQ during the first of the 2-cycle ERROR response, HTRANS must either stay at NONSEQ/SEQ if the transfer source is ignoring the ERROR, or it must change to IDLE if the source decides to cancel the next indicated transfer to respond to the ERROR.