| 摘要 |
PURPOSE:To prevent the read-out of a wrong data, by comparing charged voltage of a capacitor for backing up a data of an RAM when an electric power supply is turned on, with reference voltage of a comparator, and displaying disappearance of a data. CONSTITUTION:A CPU10 reads out a necessary data from an RAM18 and operates it, and after that, when a switch 12 connected to a main electric power supply Vcc is opened, the data of the RAM18 is held by charged voltage of a capacitor 44 of an electric power supply 34 for holding use. Subsequently, when the main switch 12 is closed again, a non-reverse input terminal of a comparator 40 becomes reference voltage by a resistance 38 and a Zener diode 42. This reference voltage is set in advance to minimum voltage for holding a data of the RAM18, and when terminal voltage of a capacitor 13 is <= reference voltage, an output of the comparaotor 40 becomes H level, and the CPU10 outputs a control signal of H level. Subsequently, and use of a wrong data is prevented by displaying the fact that a data of the RAM18 has disappeared, on the indicator. |
