13.3.2.5.3 Round-Robin Scheduling

To avoid "starvation" for priority level 0 (LVL0) interrupt requests with static priority, i.e. some interrupts might never be served, the CPUINT offers round-robin scheduling for LVL0 interrupts.

Round-robin scheduling for LVL0 interrupt requests is enabled by writing a '1' to the Round-Robin Priority Enable bit (LVL0RR) in the Control A register (CPUINT.CTRLA).

When round-robin scheduling is enabled, the interrupt vector address for the last acknowledged LVL0 interrupt will have the lowest priority the next time one or more LVL0 interrupts are requested, as illustrated in the figure below.