| 摘要 |
PURPOSE:To prevent data in a non-volatile memory from the generating an error by forming a traveling distance calculating means, the non-volatile memory, a traveling distance data updating means, a power supply circuit, a switching means, a power supply limiting means, etc. CONSTITUTION:A pulse signal from a car speed sensor 1 is counted up by the traveling distance calculating means 2. Traveling distance data are stored in the non-volatile memory 3 and applied to the means 2. Every time when the counted distance reaches a prescribed distance, the updating means 4 updates the traveling distance data stored in the memory 3. Even if an ignition switch 5 is opened, electric power is selectively supplied by a power supply circuit 6 without being passed through the switch 5. If the opening of the switch 5 is detected at the updating of the data, the switching means 8 is driven by a power supply control means 7 during the updating of the data to supply power from the battery 9 mounted on a car to a power supply circuit 6. Even if the switch 5 is opened, the data in the memory 3 can be updated and no error is generated in the data of the memory 3.
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