EXTERNAL STORAGE DEVICE

PURPOSE:To improve prevention of erroneous write and prevention of waste of a battery by providing a pull-up means for pulling up an input side control signal line to an input side of a power source control circuit, and a capacity and a pull-down means inserted between the power source control circuit and a ground. CONSTITUTION:When a voltage is supplied to a power source VCC from a system main body, input side control signal lines 107-109 become a pull-up state by resistances R1-R3. In such a state, in the case, drawing occurs, it does not occur that each input side control signal line 107-109 become an 'L' level. immediately after drawing is executed, but a stand-by state is held for a while, and when a voltage of a power source input terminal VIN does not become below a set value of a power source reset IC IC1, an RST bar terminal of the power source reset IC IC1 is varied from an 'H' level to an 'L' level. Also, a power source output terminal VOUT becomes open, and after charge of a capacitor C2 is discharged, the input side control lines 107-109 are stabilized in a 'L' level by a pull-down resistance R4.