| 摘要 |
PURPOSE:To prevent previously the system breakdown by providing a memory for storage of the retrial information into an arithmetic part, giving +1 to the memory contents in case the retrial is performed for each access given to an input/output part. CONSTITUTION:A programmable controller PC contains an input/output part 1 including plural input and output modules 11 and 12 and an arithmetic part 2 that controls the part 1. Then an external device is connected directly to the PC. A memory part 23 is provided within a memory part 22 of the part 2 to store the retrial information in addition to a sequence program. Thus the part 2 executes the input/output actions to check whether a normal action was carried or not. If no normal action was carried out, the 1st retrial is performed for decision of a normal state, etc. While in a normal action mode +1 is given to the part 23. Then +1 is given to a counter in a faulty mode. The contents of the part 23 are checked every fixed period of time together with comparison. Thus the state of the part 23 is known. |
