| 摘要 |
PURPOSE:To install a process input part ad a process output part to a place which has been separated from a CPU, by providing a watch dog timer (WDT) on a block unit of an IO, and impressing a power source for process output for the first time, after an access has been executed normally from a CPU in the process output side. CONSTITUTION:A power source for driving an output relay 13c for a process control is given by a power source 4 for process input. This power source generates by an interface circuit 13a a signal for confirming a fact that an access has been executed normally from a CPU 11, and drives a WDT circuit 130. The WDT 130 drives a transistor 131 for a prescribed time after the access has been executed normally, a relay 132 is driven and a contact 133 becomes on, and a power source 3 for process output is impressed to a process output. If the CPU or the process output part becomes abnormal and the WDT 130 is not brought to an access exceeding a prescribed time, the WDT becomes time-up, the transistor 131 becomes off, the contact point 133 becomes off, an output contact point 13d becomes off automatically, and a runaway, etc., of the process are prevented.
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