SWRU626 December 2025 CC3501E , CC3551E
The NVIC supports software assigned priority levels. A priority level from 0 to 8 can be assign to an interrupt by writing to the most significant bits of the PRI_N field in the NVIC.NVIC_IPRn register corresponding to the interrupt, see Section 3.9.11.
Only the group priority determines pre-emption of interrupt exceptions. When the processor is executing an interrupt exception handler, another interrupt with the same group priority as the interrupt being handled does not pre-empt the handler.
If multiple pending interrupts have the same group priority, the subpriority field determines the order in which the interrupts are processed. If multiple pending interrupts have the same group priority and subpriority, the interrupt with the lowest IRQ number is processed first.
If a pending Secure exception and a pending Non-secure exception both have the same group priority field value, the same subpriority field value, and the same exception number, the Secure exception takes precedence.