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AHB Bufferable/Non-bufferable write

Hariprem Arora
Note: This was originally posted on 12th September 2008 at http://forums.arm.com

Hi,

Please clarify the following issue related to AHB write:

If HPROT[2] = 1, AHB write is bufferable and we need to provide OKAY response as soon as the AHB slave interface receives data without caring that the data is actually written into the memory or not.

if HPROT[2] = 0, AHB write is non-bufferable, AHB slave interface needs to provide response to the master only when the data is actually written into the memory.

The issue is that if we see this non-bufferable transaction, the state of HRESP will by default be OKAY (HREADY is HIGH to accept the next data) and it means that we are providing the response in advance for non-bufferable write.

Please clarify how to distinguish between the two transactions.
If possible, please provide waveforms for INCR undefined length & non-bufferable write
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    Note: This was originally posted on 15th September 2008 at http://forums.arm.com

    Hi JD,

    Thanks for the detailed information.

    For non-bufferable write, you have mentioned :

    >Yes, that is the risk with providing the early response, if the destination slave    >decides on a different response you cannot change anything.

    I need to know what kind of strategy needs to be employed if destination slave has different response than the early response provided by AHB slave interface.

    How AHB master takes action in this case.

    Hari
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  • 0
    Note: This was originally posted on 15th September 2008 at http://forums.arm.com

    Hi JD,

    Thanks for the detailed information.

    For non-bufferable write, you have mentioned :

    >Yes, that is the risk with providing the early response, if the destination slave    >decides on a different response you cannot change anything.

    I need to know what kind of strategy needs to be employed if destination slave has different response than the early response provided by AHB slave interface.

    How AHB master takes action in this case.

    Hari
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