| 摘要 |
When an on-board power source is turned off, after a predetermined time has elapsed, a microcomputer 34 writes predetermined data in a nonvolatile memory 35, and when the on-board power source is turned on, the microcomputer 34 judges whether the predetermined data is written in the nonvolatile memory 35 or not. If the judgment shows that the predetermined data is not written in the nonvolatile memory 35, the microcomputer 34 determines a backup capacitor 32 not to be working normally. The predetermined time is shorter than the operating time of the microcomputer 34 determined by the discharge time of the backup capacitor when the backup capacitor is working normally, and is longer than the operating time of the microcomputer 34 determined by the discharge time of the backup capacitor when the backup capacitor is not working normally.
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