How is the PREADY signal triggered low by the Slave in an APB?


I was trying to understand the state machine of an APB. I was curious on how the PREADY signal is triggered low so that it can exit from  the ACCESS state? 

If anyone could help me with this basic question, it'll be of great help thank you. :)

  • Not sure I understand your question.

    If the peripheral is driving PREADY low, this means it is adding wait states to extend the ACCESS state, not exit it.

    When the peripheral can complete the requested transfer it will drive PREADY high, and then on the next PCLK rising edge the state machine will move to either IDLE or SETUP.

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