| 摘要 |
PURPOSE:To stabilize a data back-up action by separating selectively the pulled-up resistances from a selection signal terminal via a logical means for output of a voltage detecting circuit while an electronic circuit device is connected to an equipment main body and at the same time the power supply of the equipment main body is kept turned off. CONSTITUTION:When a power supply VCC is turned on, the output 5a of a voltage detecting circuit 5 is set at a high level and the inverter output 7a is inverted. A PMOS transistor TR7 is turned on only when the output 7a has a low level and connects a pull-up resistance Rp8 to a power supply VDD12 of an electronic circuit. Under such conditions, the selection signal input CE3 is valid and the control is possible via a main body equipment. When the VCC is turned off, the output 5a and the output 7a are set at a low level and a high level, respectively. Thus the TR7 is turned off and the resistance 8 is separated from the VDD. Then an SRAM 11 is backed up by a battery 6.
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