| 摘要 |
PURPOSE:To extend a holding time of memory contents with a small-capacity backup capacitor by detecting the reduction of a supply voltage to stop a reference clock signal and reducing the current consumption. CONSTITUTION:A device consists of a CMOS integrated circuit and is provided with a CPU 1 which performs the data processing, a ROM 2 where an operation program is written, a non-volatile memory RAM 3 where collected data is stored, an OSC 4 which generates the clock signal which determines the operation timing of the CPU 1, a battery 5 which is a driving power source, a capacitor 6 which is a backup power source of the RAM 3, a data input device 70, a data output device 71, a supply voltage detecting circuit DCTR 11 which detects the reduction of the supply voltage for replacement of the battery, and a changeover switch 12. The DCTR 11 detects detachment or insertion of the battery 5 by the voltage and switches the changeover switch 11 by a frequency switching signal 21 to switch the clock frequency of the CPU 1 from fR30 to fO32. Thus, the current consumption of the whole of the circuit is reduced.
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