Patent ID: 8060769

Claim:
The duplexed field controller including first and second control units between which a control authority is switchable, the controller characterized by comprising; a first application clock that is updated based on a reference clock so as to define a timing of an application operation of the first control unit; a second application clock that is updated based on the reference clock so as to define a timing of an application operation of the second control unit; and an update control unit that bypasses the first update of the second application clock that is based on the reference clock after switching of the control authority, if the first application clock is ahead of the second application clock when the control authority is switched from the first control unit to the second control unit, characterized in that the reference clock is transferred from a control-side control unit of one of the first and second control units to a standby-side control unit of the other of the first and second control units, and the standby side control unit updates the application clock based on the transferred reference clock.