SLAZ279AA October 2012 – May 2021 MSP430F5418
SYS Module
Functional
UNMI ISR executes twice
If a running User NMI interrupt service routine is interrupted by a SYSNMI interrupt before the respective USERNMI flag is cleared (NMIIFG, OFIFG, or ACCVIFG) the SYSNMI ISR will be executed, the UNMI ISR will complete, then the UNMI ISR will be executed a second time.
A common NMI handler can be written where the SNMI and UNMI Interrupt Vectors point to the same function. This common NMI handler must manually clear both types of pending NMI sources (User and System) to avoid double execution of the UNMI ISR.