COMMUNICATION DEVICE AND COMMUNICATION METHOD FOR PLANT CONTROL SYSTEM

A plant control system and communication method are capable of immediately dealing with wrong address settings created due to a human error during the execution of an opening procedure. In the plant control system, a higher-level device and a plurality of communication terminal devices are connected to each other through a communication path. Prior to the start of communication, a communication opening process of sequentially transmitting a call signal from the higher-level device to the terminal devices and acknowledging response signals therefrom is executed, which is followed by sequentially transmitting a call signal from the higher-level device to the terminal devices and receiving response signals from the terminal devices. The communication terminal devices compare addresses of the response signals returned from the other terminal devices to the higher-level device against an address set for local terminal devices. If a duplicate address exists, communication from the local terminal device is locked.