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needs some clarification

bala devi

Hi

i have one doubt..in apb protocols...what is the difference between wait_state and no_wait_state in apb protocopls?

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  • +1

    Sections 3.1.1 and 3.3.1 of the APB protocol document describe transfers with no wait states (when PREADY is high while PENABLE is high), and 3.1.2 and 3.3.2 describe transfer with wait states (when PREADY goes low for all but the last cycle of the PENABLE high period).

    PREADY is a signal added to the AMBA 3 APB protocol to allow the peripheral to extend the "ACCESS" phase of the APB transfer, so adding wait states when PREADY is driven low.

    PREADY is only considered by the APB master during the ACCESS phase, so outside of this period it will be ignored, hence being shown as high or low at these times.

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  • +1

    Sections 3.1.1 and 3.3.1 of the APB protocol document describe transfers with no wait states (when PREADY is high while PENABLE is high), and 3.1.2 and 3.3.2 describe transfer with wait states (when PREADY goes low for all but the last cycle of the PENABLE high period).

    PREADY is a signal added to the AMBA 3 APB protocol to allow the peripheral to extend the "ACCESS" phase of the APB transfer, so adding wait states when PREADY is driven low.

    PREADY is only considered by the APB master during the ACCESS phase, so outside of this period it will be ignored, hence being shown as high or low at these times.

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