监控系统中S7-200系列PLC的通信协议设计

Designed of Communication Protocol With S7-200 PLC for Supervisory Control System

S7-200系列PLC自由口通信方式可用于PC机对PLC的监控,现有的S7-200系列PLC通信协议要么针对某一具体控制系统,要么比较复杂,理解困难,使用不便,通用性不强。本文利用S7-200系列PLC自由口通信方式中灵活的接收控制功能,设计了简单、可靠的通信协议,实现了简易、高效、通用性强,便于移植的通信程序。协议采用十六进制,发送和接收协议格式类似,字节数固定,通过变量寄存器可读写PLC中任何存储器中的数据,便于实现PC机对PLC的远程监控。

The free-port communication mode of S7-200 PLC can be used for monitoring PLC with PC in the supervisory control system, all existing communication protocols using for special application or it is too complex to understand and application.This paper uses flexible function of receive message control of S7-200 PLC’s freeport mode, designs a simple, reliable communication protocol, programs a high-performance, universal communication routine simply and easily , and easily using to special application .This protocol is hexadecimal , sending format as like as receive, fixed bytes, can read and write any register of PLC, so that it easy use for monitoring PLC with PC.