| 摘要 |
PROBLEM TO BE SOLVED: To provide a programmable logic controller for saving data to a nonvolatile memory without storing data in a volatile memory by a battery when a user shuts down power supply intentionally. SOLUTION: A programmable logic controller including a volatile memory 12, a backup circuit 30 storing data in the memory 12 when the power supply is stopped, a nonvolatile memory 13, and a switch 31 to be operated by a user. The controller determines whether power supply is shut off by the operation of the switch 31, and stores the determination result even after the shutdown. If the shutdown has been caused by the operation of the switch 31, the controller saves the data in the memory 12 to the memory 13, and also stops voltage application to the memory 12. If the shutdown has not been caused by the operation of the switch 31, the controller applies a battery voltage to the memory 12, and when starting the power source, if the previous power supply shutdown has been caused by the operation of the switch 31, the controller restores the data, which has been saved to the memory 13, to the memory 12. COPYRIGHT: (C)2009,JPO&INPIT
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