| 摘要 |
<p>PURPOSE:To easily and effectively attain power saving, by supplying power only when it is detected that an operation control signal to operate a prescribed part to be power-saved is supplied to the part. CONSTITUTION:A ROM4 of N-channel is taken up as the object of a circuit part to be power-saved in which a considerable large amount of power is consumed. Before an access signal 6 is supplied to the ROM4, a power source control circuit 3 is controlled by supplying a power source control signal 7 to the power source control circuit 3, and a power source voltage is supplied to the ROM4. When the power source voltage is supplied to the ROM4 under the control of a discrimination circuit 2 through the power source control circuit 3, the discrimination circuit 2 supplies the access signal 6 to the ROM4. After the access signal 6 is supplied to the ROM4, and a bit of information is read out, no more bit of bank information 10 from a system part 1 is present, and when a ROM selection control signal 11 goes to a level O, the supplying of the access signal 6 to the ROM4 is also ceased, and a transistor 23 is turned off, and the supplying of the power source voltage to the ROM4 is stopped.</p> |
