| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect the abnormality of the whole control device including other parts in addition to a control body part. SOLUTION: A clock generating program is prepared by a sequence program (such as a ladder program) and stored in a program memory 212b provided in a CPU 21 of an PLC body part 2. In input/output units 23-25 (I/O equipment) and remote I/O R1-Rn (I/O equipment), a clock output circuit C outputs clock on the basis of ON-OFF data supplied by the execution of the program, and when a watchdog timer T is reset by the clock during a fixed cycle, the normal operation of each part up to the I/O equipment is confirmed. If the watchdog timer T is not reset by the clock during the fixed cycle, it is confirmed that there is abnormality at some pat on the way to the I/O equipment.</p> |
