下面是IAR的例子中的程序，我在看这个，总觉的搞错了，
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
NVIC_InitStructure.NVIC_IRQChannel = EXTI2_IRQChannel;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
在程序中NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);是设置优先级分组，选的是组1先占优先级1位，从优先级3位。那NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;是什么意思？我认为NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority只能为0或1，怎么能为2呢？ |
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