| 摘要 |
PURPOSE:To back up data without fail even when any unexpected condition such as the exhaustion of a main power source, the defect of contact or the run-away of a CPU, etc., is generated in the middle of writing the data. CONSTITUTION:Plural backup memories 32a and 32b are provided while being mapped to mutually different addresses and being independent each other. The data are cyclically written to the respective backup memories. When reading the backup data, it is checked whether the backup data of the respective memories are normal or abnormal, and the backup data are read out from the memory judged normal. Thus, even when any abnormality is generated in the case of writing data to the backup memory defined as a write object at a present, the normally written backup data is remained at the remaining memory, which is not defined as the write object at present, and the reliability of the data backup is considerably improved. |
