PROBLEM TO BE SOLVED: To provide a programmable controller unit which can detect data destruction of a memory rapidly and accurately, and which can automatically restore while continuing operation of system when memory abnormality of data destruction is detected.;SOLUTION: The unit is provided with a user program memory 14 storing a user program to be read out at the time of calculation processing and a backup memory 15 storing data with the same contents as the user program stored in the user program memory. The unit judges whether a memory abnormality exists or not comparing user data stored in the user memory 14 and the backup memory 15 while cyclic execution. When a memory abnormality is detected, data at the position where memory abnormality is detected is restored with the data at the corresponding position of the backup memory and the cyclic execution is continued thereafter.;COPYRIGHT: (C)2006,JPO&NCIPI
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