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SC and SD states in case of ReadNoSnoop transactions

Hi All,

This question is regarding "ReadNoSnoop" transaction of AMBA- ACE protocol.

If "ReadNoSnoop" transaction is used in a region of memory that is not shareable with other masters, then how can the cache line have have "Shared Clean" or "Shared Dirty" state as its starting state for "ReadNoSnoop" transaction?

Please have a look at the table C4-2 "Other permitted ReadNoSnoop cache line state changes" on page no. C4-197 in ACE SPEC Document "ARM IHI 0022E".

Top replies

Christopher Tory over 9 years ago +1 verified

Firstly, these line transitions starting from a Shared state are the 'Permitted' transitions, not the 'Expected' ones. A 'Permitted' usage is legal with regards to maintaining coherency, but is not expected...