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Is access to memory Atomic ?

Honored Contributor II



Is access to memory 32-bit atomic ? 

We plan to use shared memory between ARM and Nios on same FPGA (Arria V). 

Can we assume that the access to memory of read/write is atomic 32-bit ? 


Thank you, 

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2 Replies
Honored Contributor II

Your memory ic data width is 32 bit?

Honored Contributor II

Depends on what you mean by atomic. If you mean whether a 32-bit access will become corrupted by the other CPU then answer is no if they perform aligned 32-bit accesses. But if you are looking to perform a mutually exclusive access where you lock down a memory location (mutex) the only HPS memory that supports this is the SDRAM controller and Nios II doesn't have to ability to generate AXI traffic to perform a mutex access. You could add this ability fairly easy but making a custom instruction that exposes an AXI master to perform the mutex access into the HPS SDRAM though. 


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