C51单片机，超声波模块程序，通过外部中断获取上升沿时间，判断距离-C51 microcontroller, ultrasonic module program, by external interrupt obtain rising time, determine the distance

用C语言编写的超声波脉冲发射程序和接受程序，以c51单片机为控制器(The ultrasonic pulse transmitting program and receiving program written in C language are used as the controller of C51 single chip microcompute)