STM32 interrupt concept and understanding

1. STM32 reduces the register bits for specifying interrupt priority to 4 bits. The grouping of these 4 register bits is as follows:

Group 0: All 4 bits are used to specify the response priority

Group 1: The highest bit is used to specify the preemptive priority, and the lowest 3 bits are used to specify the response priority

Group 2: The highest 2 bits are used to specify the preemptive priority, and the lowest 2 bits are used to specify the response priority

Group 3: The highest 3 bits are used to specify the preemptive priority, and the lowest 1 bit is used to specify the response priority

Group 4: All 4 bits are used to specify preemptive priority

//Set up NVIC

//NVIC_PreemptionPriority: preemption priority

//NVIC_SubPriority: response priority

//NVIC_Channel: interrupt number

//NVIC_Group: interrupt group 0~4

//Note that the priority cannot exceed the range of the set group! Otherwise, there will be unexpected errors

2. Priority

1. A high-priority preemption priority can interrupt an ongoing low-priority preemption interrupt. 

2. Preempt interrupts with the same priority level. Interrupts with higher priority levels cannot interrupt interrupts with lower priority levels. 

3. Preempt interrupts with the same priority. When two interrupts occur at the same time, the one with higher response priority will be executed first. 

4. If the preemption priority and response priority of two interrupts are the same, the interrupt that occurs first will be executed first.