| 摘要 |
PURPOSE:To obtain a data back-up circuit with a small quantity of power consumption by detecting drop of the level of power source voltage, saving the data in the first memory to the second memory for preservation when the level of the power source voltage drops, and returning it when the level of the power source voltage rises. CONSTITUTION:When a main action 10 drops to a prescribed voltage or below, a voltage detecting circuit 11 detects this and the control signal of the effect is outputted to respective circuits. By reading successively the data in a RAM 1 and writing them to E<2>PROM 2, the data transfer is executed. When a main electric power source 10 outputs a voltage 5V, the voltage detecting circuit 11 detects this, outputs a control signal to respective circuits, a control circuit 15 successively reads the data in the E<2>PROM 2 in accordance with the address of an address counter and writes them to the RAM 1. Only during the time of transferring from the RAM 1 to the E<2>PROM 2, an auxiliary power source 13 comes to be an ON condition, and therefore, the power consumption comes to be very small. |
