| 摘要 |
<p>PURPOSE:To enable with a simple circuit to prevent memory contents from being destroyed when turn on an electric power supply or the power supply is turned off, by making the selection line of a memory circuit unselected when a power voltage is lower than a reference value. CONSTITUTION:A power-on resetting circuit A which generates a reset signal when a power supply is turned on and has a time constant depending upon a resistance R3 and a capacitor C1 is provided and the memory protecting circuit of a memory circuit 2 which is powered down by a battery BA is provided with a detecting circuit which detects a power voltage Vcc exceeding a prescribed reference value. Then when the power voltage Vcc is lower than the reference value, the capacitor C1 is discharged and at the same time, the selection line of the memory circuit 2 is made unselected. For example, a circuit which includes a microcomputer 1, a Zener diode ZD, etc., as shown in the figure is used to perform said operation.</p> |
