| 摘要 |
PURPOSE:To simplify a station by reducing a load on software by delaying the operation of a relay when a main controller recovers from a fault by using an R-S flip-flop, and stopping the recovery of a watch dog timer during the period. CONSTITUTION:When a main controller 1 is shut down and a watch dog timer WDT detects that, a transistor 11 turns off and a collector output WDTM from the controller 1 goes up to a 1. Consequently, the output R of an R-S FF41 goes up to the 1, the S goes down to a 0, and the output -Q goes up to the 1 to turn on a relay RY, switching contacts S1 and S2 to terminals (b). An operation terminal 3 is threrefore connected to the side of a subordinate controller 2. If the controller 1 recovers during the control of the controller 2, its WDT recovers, but the FF41 has the R and S helt at the 0, so the operation terminal 3 is still connected to the controller 2 side, so that the operation is continued still under the control of the controller 2. |
