All interrupt vectors are assigned to one of three possible priority levels, as
shown in the table below. 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 15-2. Interrupt Priority Levels| Priority | Level | Source |
|---|
| Highest | Non-Maskable Interrupt | Device-dependent and statically assigned |
| ... | Level 1 (high priority) | One vector is optionally user selectable as level 1 |
| Lowest | Level 0 (normal priority) | The remaining interrupt vectors |
