在实验中发现一个奇怪的情况，将NVIC的抢占优先级设置为0X10，为何中断也能正常工作？程序如下：
/*设置NVIC中断优先级*/
NVIC_InitStruct.NVIC_IRQChannel=EXTI0_IRQn;//外部中断0
NVIC_InitStruct.NVIC_IRQChannelCmd=ENABLE;
NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority=0x00;
NVIC_InitStruct.NVIC_IRQChannelSubPriority= 0x10;
NVIC_Init(&NVIC_InitStruct);
NVIC_InitStruct.NVIC_IRQChannel=EXTI2_IRQn;//外部中断2
NVIC_InitStruct.NVIC_IRQChannelCmd=ENABLE;
NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority=0x01;//抢占优先级为1
NVIC_InitStruct.NVIC_IRQChannelSubPriority= 0x10;
NVIC_Init(&NVIC_InitStruct);
NVIC_InitStruct.NVIC_IRQChannel=EXTI3_IRQn;//外部中断3
NVIC_InitStruct.NVIC_IRQChannelCmd=ENABLE;
NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority=0x10;
NVIC_InitStruct.NVIC_IRQChannelSubPriority= 0x10;
NVIC_Init(&NVIC_InitStruct);
主函数设置为：NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);//设置系统中断优先级分组为2，即2为抢占优先级和2位响应优先级
为何将抢占优先级和响应优先级设置为0x10，中断也能正常工作？？？响应优先级和抢占优先级不应该都在0~3内么？？还是我理解错了？？
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然后，不管你把抢占优先级和子优先级设成什么值，通过组合运算后，只会取结果的1个字节的高4位。
这就是为什么你把优先级写为0x10也会运行并响应中断。
assert_param(IS_NVIC_PREEMPTION_PRIORITY(NVIC_InitStruct->NVIC_IRQChannelPreemptionPriority)); //在NVIC_Init（）函数中
这句的有效性判断为#define IS_NVIC_PREEMPTION_PRIORITY(PRIORITY) ((PRIORITY) < 0x10)，为何当我NVIC_IRQChannelPreemptionPriority = 0x10；时不报错，既然都不满足有效性判断，按理说不能正常运行呀
因为没有使能assert功能,在stm32fxxx_conf.h中
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