By way of data monitor and analyze, found out the keyframes format of PPI protocol on Siemens S7-200 series PLC,it can be use in communication of upper computer,field device with a PLC.

• 通过数据监视、分析的方法,找出了西门子S7-200系列PLC的PPI协议关键帧格式,可用于上位机、现场设备与PLC之间通讯。