METHOD FOR DIAGNOSIS BY PULLING-OUT OF SIGNAL INPUT/ OUTPUT CONNECTOR CABLE IN AUTOMATIC CONTROLLER

PURPOSE:To set only the operation end, which is affected by pulling-out, to the safe state and continue automatic operation in the other operation ends by diagnosing the pulling-out state of a connector cable in every analog and digital signal input/output module (PIO). CONSTITUTION:A prescribed voltage signal 84 is outputted from the inside of a PIO 2 to an input/output unit 3 through connectors 41 and 43 and a cable 42 and is taken into the PIO 2 again and is connected to a photocoupler 25. A CPU 1 outputs a connector cable pulling-out diagnostic address signal to an address bus 5 and leads an R/W signal 7. In the PIO 2, it is decided by an address coincidence detecting circuit 23 that connector cable diagnosis is selected, and a connector cable diagnostic result output selecting a signal 81 is set to the high level. A connector cable diagnosis result signal 83 is outputted to a specific signal line 61 of a data bus 6 through a NAND gate 24. The CPU 1 detects pulling-out of the connector cable in accordance with the state of the signal line 61 of the bus 6.