| 摘要 |
PURPOSE:To make provision against a fault of an input unit by providing several input units with a substitute input unit which can be used as any input unit. CONSTITUTION:In the sequence controller in the figure, processing part 11 connected to memory 10 stroed with a sequence program attains access to input-output units IU1-IUn and OU1-OUn via unit selector 12 for normal operation. If IU1, for example, gets ou of order, leads of its input contact PS10, and PS11... are reconnected to substitute input unit 20. Then, the address of IU1 is set to address setter ASP1 of substitute input unit 20. Once access to troubled unit IU1 is attained by processing part 11, a coincidence signal from comparator 23 changes circuit 21 over to input an input signal from substitute input unit 20 to processing part 11. |
