我们先来看一下Reference Datasheet中是如何说的：

SCB->AIRCR中目前只用到4位，也就是最高能有16级中断嵌套，如果全使用的话可以达到256级

选用优先级分组(实际就是选几位用于主优先级几位用于辅优先级)

注意，我们在一个工程中只能用一种分组方式

The table below gives the allowed values of the pre-emption priority and subpriority according

to the Priority Grouping configuration performed by NVIC_PriorityGroupConfig function

===========================================================================

NVIC_PriorityGroup | NVIC_IRQChannelPreemptionPriority | NVIC_IRQChannelSubPriority | Description

===========================================================================

NVIC_PriorityGroup_0 | 0 | 0-15 | 0 bits for pre-emption priority

|| | 4 bits for subpriority

----------------------------------------------------------------------------------------------------------------------------

NVIC_PriorityGroup_1 | 0-1| 0-7 | 1 bits for pre-emption priority

||| 3 bits for subpriority

----------------------------------------------------------------------------------------------------------------------------

NVIC_PriorityGroup_2 | 0-3 | 0-3 | 2 bits for pre-emption priority

|| | 2 bits for subpriority

----------------------------------------------------------------------------------------------------------------------------

NVIC_PriorityGroup_3 | 0-7 | 0-1 | 3 bits for pre-emption priority

| | | 1 bits for subpriority

----------------------------------------------------------------------------------------------------------------------------

NVIC_PriorityGroup_4 | 0-15| 0 | 4 bits for pre-emption priority

|| | 0 bits for subpriority

以上是我提取库中misc.h中的说明便于大家理解

如果要使用中断那就得把中断向量表先存储到存储器，我们先来一段程序看一下吧

void NVIC_Configuration(void)

{

NVIC_InitTypeDef NVIC_InitStructure;

#ifdef VECT_TAB_RAM

NVIC_SetVectorTable(NVIC_VectTab_RAM,0x0);

#else

NVIC_SetVectorTable(NVIC_VectTab_FLASH,0x0);

#endif

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);

NVIC_InitStructure.NVIC_IRQChannel = EXTI15_10_IRQChannel;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

}

这里边包含一个条件编译，如果我们要把中断向量表存储在RAM或者FLASH就要定义相关的宏

后边选用优先级分组的0组，也就是0位用于主优先级，4位用于辅优先级

主优先级可以中断嵌套(可以抢占)

辅优先级不可以中断嵌套，只能当前中断完成之后再相应优先级最高的

如果辅优先级相同则相应中断向量表靠前的

NVIC_IRQChannel 是说明用的哪种中断，包括所有的中断与异常(NVIC都管理，包括内核的)

讲到这里我们要提一下不可屏蔽中断，这个中断是不能屏蔽的NMI是不能屏蔽的，其他中断都是可以屏蔽的