| 摘要 |
PURPOSE:To prevent memory data during updation from being lost, even the interruption of a main power source (battery) occurs without an auxiliary power source (battery) by using charge stored in a capacitor as a power source and maintaining its output voltage. CONSTITUTION:In the case power source interruption is generated in a state that a main power source 1 is turned on, the power source interruption is detected in a power source interruption detecting circuit 5 and an interruption signal is sent out to a CPU 6. Then the CPU 6 executes an interruption processing and in the case the data of a memory (EEPROM) 7 are being updated, the updating processing is continued. In a period until the foregoing processing is finished, the power source for the power source interruption detecting circuit 5, the CPU 6 and the memory 7 obtain output voltage from the output of a maintaining power supply 4 for, based on the energy of a capacitor 3 charged through a charge reverse current stopping diode 2 from the main power source 1 until power source interruption is generated. The capacity value of the capacitor 3 is determined from the length of the time required for a processing for writing data in the memory 7. |
