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Why do we have to send HMASTLOCK signal to the slave?

In AHB-Lite cases, every transfer starts with address phase with signals from master.

And also in multi-master cases, arbiter decides with whether it can GRANT bus access to other masters or not.

So, I think it's fine to only let masters or arbiters to know whether it is locked sequence or not.

However, on the document HMASTERLOCK signal is sent to slave.

Why do we need this?

Is there any cases slaves use HMASTERLOCK signal for?

  • Hello Hyunkyu,

    The answer to your question can be found in the AHB-Lite specification (ARM IHI 0033A).

    3.3 Locked transfers

    Most slaves have no requirement to implement HMASTLOCK because they are only
    capable of performing transfers in the order they are received. Slaves that can be
    accessed by more than one master, for example, a Multi-Port Memory Controller
    (MPMC) must implement the HMASTLOCK signal.

    Regards,

    Xingguang