NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3;
        NVIC_InitStructure.NVIC_IRQChannelSubPriority =3;               
        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;                       
        NVIC_Init(&NVIC_InitStructure);

        USART2连了MAX485模块，这样的话接收到数据产生中断是外部中断还是内部中断？
        外部中断和内部中断有什么区别？
        谢大神指教