FSMC access thread safe?

[Ingmar]

Supposed I am using external memory via an 16 bit address / 8 bit data bus with FSMC (STM32F714). An RTOS is running.

Is access to this memory atomic (in the sense of thread safety) when I read/write 32 bit wide data? The consideration is, for instance:

• bytes 1 and 2 are already written, then a task switch occurs, and another task uses the FSMC controller for a different read/write operation;
• worse: the second task accesses the same memory location, thus overriding all 4 bytes, and then, when the former task continues, it finishes writing bytes 3 and 4.

Can the processor handle these operations atomically, or is usage of a mutex appropriate when accessing the same resource (external memory, or the FSMC infrastructure as a whole)?

[waclawek.jan]

> STM32F714

?

Yes, FSMC/FMC writes are atomic, even if they are split internally because of narrow external bus.

JW

[Ingmar]

good news, thank you Jan!