14.3.2.4 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 14-2. 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