Understanding of arm interrupt priority

        The interruption of MCU is divided into preemptive priority and response priority （ Sub priority ）, When interrupting, the preemption priority first determines which interrupt is generated .

      Preemption priority is higher than response priority . The smaller the value, the higher the priority .

       High preemptive priority can interrupt low preemptive priority , Hence the name preemption ; When the preemptive priority is the same , The higher the response priority , If it happens at the same time, respond to it first , But don't interrupt low response priority , Response expresses response speed .

         In explaining the two points here ： First of all , If the preemption priority and response priority of two interrupts are the same , It depends on which interrupt occurs first ; second , High priority preemption priority can interrupt the ongoing low preemption priority interrupt . And preempt interrupts with the same priority , A higher priority response priority cannot interrupt an interrupt with a lower response priority .
         Let's illustrate with examples ： Suppose the interrupt priority group is set to 2, Then set the interrupt 3(RTC_WKUP interrupt ) The preemption priority of is 2, The response priority is 1. interrupt 6（ External interrupt 0） The preemption priority of is 3, The response priority is 0. interrupt 7（ External interrupt 1） The preemption priority of is 2, The response priority is 0. So this 3 The priority order of interrupts is ： interrupt 7> interrupt 3> interrupt 6.

        Preemption priority and response priority , In fact, an interrupt contains two priorities , The former is the level division of preemption priority , The latter is the priority division of the same preemption priority .
        such as ： interrupt A Preemption priority ratio B high , that A Can be interrupted in B Trigger inside , Ignore response priority
A and B Preemption priority is the same , be A、B The response priority of determines who responds first .
 

Reference resources ：https://blog.csdn.net/lr1916417519/article/details/81057810

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