13.3.2.4 Interrupt Level
The interrupt level is default on level 0 (normal) for all interrupt sources. It is possible to select one interrupt source to level 1 (high) by writing interrupt address to CPUINT.LVL1VEC register. This source will have higher priority than normal level interrupts.
An interrupt request from a level 1 source will interrupt any ongoing interrupt handler from a level 0 interrupt. When returning from the level 1 interrupt handler, the execution of the level 0 interrupt handler will continue.