MSP430FR2433: Shall a variable made PERSISTENT() or NOINIT() be specified as volatile?

Hi Thomas,

It depends on how the variables will be used.

A variable should be declared volatile whenever its value could change unexpectedly. In practice, only three types of variables could change:

• Memory-mapped peripheral registers (peripheral registers)
• Global variables modified by an interrupt service routine
• Global variables within a multi-threaded application

PERSISTENT or NOINIT pragmas apply to variables located in non-volatile memory, FRAM in this case, and are typically protected with a write protection mechanism.  But if you have a PERSISTENT or NOINT variable that can be modified in the main thread and the ISR, you should still probably qualify them as volatile to be on the safe side.