用51单片机测试频率，采样定时器及中断，测试精准。（压缩文件中带仿真图及程序）-With 51 test frequency, sampling timer and interrupt the test precision. (Compressed file with simulation diagram and procedures)

DOS实时中断接收四路串口数据，包含时间中断计时器。-DOS interrupt receiving four road real-time serial data, including time interrupt timer.

利用单片机的内部定时器溢出产生中断来实现定时， 把单片机内部的定时/计数器0作为定时器，实现2.5ms定时。外部待测脉冲从单片机的TI（第15引脚）输入，以定时/计数器1作为计数器，利用中断方式来达到间接测量的目的。最后采用四位数码管显示-The use of MCU internal timer overflow interrupt to achieve timing, the MCU internal timer/counter 0 as a timer, the timing to a