Realization and Performance of Serial Communication between Different Kinds of PLC

Communication between different kinds of Programmable Logic Controller (PLC), especially the Serial Communication (SC) between S7-300 and FX PLC, was investigated in this paper. The approach of SC between these two kinds of PLC was researched, and the communication performance was tested. On the basis of adequate analysis to the Programmable Port Protocol (PPP) of FX PLC, we designed the SC system structure, which was linking module CP340 of S7-300 to the programmable port of FX PLC with SC-08 programmable cable. And bidirectional semi-duplex SC was realized by configuration and programming to S7-300 PLC. In order to test the communication performance, we proposed a test scheme to measure the communication delay. The reading and writing communication delay were obtained, and the experimental result will be worked as reference when designing the networked control system in this communication structure.