| 摘要 |
PURPOSE:To allow stored contents of both controllers to coincide with each other by performing the control operation at a preliminarily determined operation period each time when process data transmitted from the current controller at every control period is received by the stand-by controller. CONSTITUTION:Process data is inputted to a current controller A having the control right out of two controllers A and B from a process input/output device (PI/O) 11 at every preliminarily determined control period through a PI/O bus 10, a switching circuit 8A, and a process input/output interface (PI/OIF) 7A, and the control operation is performed. Inputted process data is transmitted to the stand-by controller B through a transmission controller 4A and a transmission interface 3A at every control period. Since the stand-by controller B performs the control operation at a preliminarily determined operation period each time when receiving process data, control operation results of both controllers coincide with each other with a phase delay.
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