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The Non-Secure Access IDentity (NSAID) of TZC-400

wangyong

Hi experts,

I get the following information about NSAID from TZC-400 trm.
The Non-Secure Access IDentity (NSAID) input identifies the source interface of a transaction to a filter unit.
When in Non-secure state the NSAID inputs identify the master that is the source of the access.
The filters use the NSAID inputs to filter Non-secure accesses based on the source of the access.
NSAIDR<x>[3:0]     Master        Identifies the source of Non-secure read accesses
NSAIDW<x>[3:0]     Master        Identifies the source of Non-secure write accesses

And I am confused about NSAID.
Why not use AXI ID signal AxID to identify the master that is the source of the access?
How to control NSAIDR<x>[3:0] and NSAIDW<x>[3:0] signals?


Best Wishes,

  • 0 Arm Employee Badge

    Hi,

    The NSAID can be any group of signals that will uniquely identify a master to the level of granularity you need. 

    In practice you will probably drive them from either the incoming AxIDs or from additional specific AxUSER bits.  Remember a master might generate a range of AxIDs depending on the transaction type so you may need to match on the common bits to map all transactions from a master to the same NSAID (if that's what you need to do.)

    The important thing is that you must have enough unique bits to identify every master that needs it's own NSAID.