| 摘要 |
PURPOSE:To guarantee the recording data of a semiconductor memory without fail by providing a power source voltage detecting circuit to cause unidirectional and bidirectional three state buffers to be a conductive condition when a power source input voltage is larger than a specified value and to cause the buffers to be an interrupted condition when it is smaller than the specified value. CONSTITUTION:When a power source input 14 achieves a normal voltage to be larger than the specified value, a power source voltage detecting circuit 21 generates a signal to contact a series transistor (TR) 20 and unidirectional and bidirectional three state buffers 18 and 19. When the input 14 is an abnormal voltage to be smaller than the specified value, or in case of a portable time, the circuit 21 generates a signal to turn off the TR 20 and the buffers 18 and 19. Since the contacting/turning-off is controlled by a card attaching and detaching signal input 23 from a terminal equipment, the storing data of the semiconductor memory are guaranteed when the card is attached and detached in the active condition of the terminal equipment and the memory card. When the input 14 is turned off and in case of the portable time, a power source current is prevented to be flowed to the terminal equipment. |
