| 摘要 |
PURPOSE:To perform effective processing without malfunction nor necessary operation and to improve the reliability of a system by deciding which of the voltage of a backup power source and a reference voltage is higher during a recovery from a power failure and then selecting a program. CONSTITUTION:The backup power source 24 generates a hold voltage VX for protecting the contents of a RAM 23 in a device which protects information in the RAM 23 during a power failure or when electric power is cut off. A reference voltage generator 29 generates the reference voltage Vref which is stable against temperature and corresponds to the lowest hold voltage. A decision device 30 compares the voltages VX and Vref with each other when the recovery from the power failure is made or when the power source is turned on again to decide whether the VX is higher than a voltage required to protect the contents of the RAM 23 or not. Programs for processing are switched on the basis of the state of the voltage VX i.e. according to whether the contents of the RAM 23 are protected or destroyed and necessary data in the contents of the RAM 23 are restored.
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