监控系统中 S7-200系列 PLC 的通信协议设计

摘要

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 su-pervisory 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 free-port mode, designs a simple, reliable communication protocol, programs a high-performance, universal commu-nication 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.