Interrupt Priority

All interrupt vectors are assigned to one of three possible priority levels as shown in the table. An interrupt request from a high priority source will interrupt any ongoing interrupt handler from a normal priority source. When returning from the high priority interrupt handler, the execution of the normal priority interrupt handler will resume.
Table 1. Interrupt Priority Levels
Priority Level Source
Highest Non-Maskable Interrupt (NMI) Device dependent and statically assigned
... High Priority (Level 1) One vector is optionally user selectable as Level 1
Lowest Normal Priority (Level 0) The remaining interrupt vectors