基于串口服务器的PLC与上位PC机的远程通讯设计

Design of TCP/IP Network Communication between Host Computer and PLC Based on Serial Server

本文介绍了在基于串口服务器的新型网络连接方式下的 PC 与 PLC 的实时通讯方法,针对西门子 S7-200PLC,给出了与上位 PC机通信原理和自由口通信协议的设计方法。该协议采用了查询方式与实时方式相结合的方式,并应用存锗区指针的间接寻址功能存取数据,实现 PLC 发送数据帧的长度可变。

This paper introduces the Network communication between host computer and PLC based on a new method of linking serial server, the communication principle to host computer and the design of freeport communication. The communication protocol uses a new mode which combines query mode and real time mode and index address which realizes the alterable length of data frame.