本文件是基于51单片机的modbus源代码包，对于进行相关开发的技术人员有很好的参考价值-This document is based on 51 microcontroller modbus source code package, have a good reference value for the associated development of the technical staff

此程序是用51单片机开发的，步进电机正反转及调速控制的程序。-This program is the development of 51 single-chip stepper motor speed control and reversing the procedure.