Siemens PPI协议分析

西门子S7-200 PLC之间或者PLC与PC之间通信有很多种方式:自由口，PPI方式，MPI方式，Profibus方式。使用自由口方式进行编程时，在上位机和PLC中都要编写数据通信程序。使用PPI协议进行通信时，PLC可以不用编程，而且可读写所有数据区，快捷方便。但是西门子公司没有公布PPI协议的格式。用户如果想使用PPI协议监控，必须购买其监控产品或第三方厂家的组态软件。这样给用户自主开发带来一定困难，特别是自行开发的现场设备就不能通过PPI协议接入PLC。其它通讯方式编程也存在编程复杂，需要购买软件和授权等局限性。通过数据监视、分析的方法，我们找出了PPI协议的关键报文格式，可用于上位机、现场设备与S7-200 CPU之间通讯。-Siemens PPI negotiates analysis

Siemens S7-200 PLCs it occasionally between PC and PLC the correspondence has a lot of methods: free orifice, PPI method, MPI method, Profibus method.Use free when the orifice method progress weave a distance all want to write data correspondence procedure in the place of honor machine and PLC.While using PPI to negotiate progress correspondence PLC can need not plait distance, and can read and write all data zones, fast convenience.But Siemens company didn t release PPI the format of agreement.If the consumer wants to use PPI to negotiate supervision, has to buy the configuration software that it supervises and controls a product or third party plant house.Give the consumer independent tapping fetch must be difficult like this, develop especially and by oneself of site equipment the incapability negotiate connecting through PPI into PLC.Other telecommunication methods