| 摘要 |
<p>PURPOSE:To extend a data holding time of an RAM, by setting an RAM holding capacity value whose set value or below is made power for holding a data, to power residual capacity of a battery. CONSTITUTION:An LSI 1 is provided with a CPU 2, an RAM 3 and an OSC 4, the CPU 2 controls each circuit device, the RAM 3 executes write and read- out of a data, and the OSC 4 generates a clock pulse. Also, the CPU 2 is provided with a counter 5. A power supply part 6 is connected to an external power supply, supplies electric power to each circuit of the LSI 1, and when this power supply part 6 is cut off, a power cut detecting part 7 detects it and inputs a power cut signal to the CPU 2. A battery 8 is connected so as to be charged from the power supply part 6, also is connected so as to back up each circuit in the LSI 1, and when said power cut signal is inputted to the CPU 2, the electric power is switched to that of the battery 8.</p> |
