MCS-51单片机有5个中断源，其中两个是由-INT0、-INT1引脚输入的外部中断源；另外三个是内部中断源即由T0、T1的溢出引起中断和串行口发送完一个字节或接收到一个字节数据引起中断。触发外部中断有两种方式，即下降沿引起中断或低电平引起中断。当编程TCON中的ITi（i=0、1）为1时，则引起触发的方式为边沿触发方式，反之(ITi=0)为低电平触发方式。每个中断源的中断请求能否得到响应要受两级“开关”的控制，即一个总“开关”-MCS-51 single-chip has five interrupt sources, two of which are by-INT0,-INT1 pin input external interrupt source　the other three internal interrupt sources from the T0, T1 overflow caused by the disruption and serial port sending or receiving end of a byte to a byte of data caused by interruption. Triggered external interrupt has two modes, namely, falling edge or low-level disruption caused disruption caused. When programming TCON in ITi (i = 0,1) for the 1:00 has been the subject of a way to trigger the way to the edge of the trigger, on the contrary (ITi = 0) for low-level trigger mode. Each interrupt source interrupt request can be subject to levels in response to