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What should be the behavior of an AHB5 slave when HNONSEC=0?

Joaquin

What should be the behavior of an AHB5 slave when:

it is trust peripheral and receives a transaction with hnonsec=1
it is trust peripheral and receives a transaction with hnonsec=0
it is not trust peripheral and receives a transaction with hnonsec=1
it is not trust peripheral and receives a transaction with hnonsec=0

Thank you very much in advance.

BR,Joaquin

  • 0 Arm Employee Badge

    This isn't quite the right way of thinking about this.

    If the slave/subordinate does not trust the device issuing the transaction, then it would likely ignore the HNONSEC signal.  In this case, this form of security in the system is broken as a device can issue secure transactions that is not trusted.

    Instead, the system should be designed such that only trusted managers can issue transactions with HNONSEC = 0.  The subordinate can then use HNONSEC to determine whether accesses can be made to a resource or memory location that the subordinate considers to be secure.