Patent ID: 7055061

Claim:
A field apparatus control system for controlling a field apparatus connected to a field bus, comprising: first and second main control units configured to control the field apparatus; and first and second communication control units configured to process information communication between the first and second main control units, respectively and the field apparatus via the field bus, wherein the first main control unit and the first communication control unit are in a normal system mode or in a standby system mode, the second main control unit and the second communication control unit are in a normal system mode or in a standby system mode, and each of the first and second communication control units have a same address on a network via the field bus, and wherein information outputted to the same address from the field apparatus via the field bus is received and processed by both the first and second communication control units, wherein each of said first and second communication control units further comprises: means for transmitting an operation request to the field apparatus based on control information when the respective communication control unit is in the normal system mode, said control information being transmitted from the corresponding main control unit; means for receiving response information corresponding to the operation request transmitted from the field apparatus to the same address so as to transmit the received response information to the corresponding main control unit; first means for judging whether or not failure occurs to the respective communication control unit and corresponding main control unit; means for stopping operation of the respective communication control unit, when the first means for judging judges that failure occurs to the respective communication control unit and the respective communication control unit is in the normal system mode; and means for monitoring the operation of a communication control unit that is in the normal system mode when the respective communication control unit is in the standby system mode, detecting a stop of operation of the communication control unit that is in the normal system mode when the respective communication control unit is in the standby system mode, and switching the respective communication control unit and corresponding main control unit to the normal system mode when the respective communication control unit and the corresponding main control unit are in the standby system mode.