| 摘要 |
PURPOSE:To protect simply the content of a memory at power fault by detecting that a power supply voltage drops to a prescribed level, and transfering automatically a data in a RAM area to a nonvolatile memory area. CONSTITUTION:The charging to an externally mounted capacitor 4 is finished during normal operation. When the power supply voltage drops and is lower than a voltage value Ej1, a switch SWa is turned off to hold a voltage stored in the capacitor 4. When the power supply voltage drops and is lower than the voltage value Ej2, a switch SWc is turned off and also a switch SWb is set and the electric charge stored in the capacitor 4 allows an internal electronic circuit 2 to transfer from the RAM area 2a to the nonvolatile memory 2b. The transfer of data is finished by allowing the internal electronic circuit itself to generate a timing pulse requested from the memory. When the transfer is finished, the switch SWc is turned on again. |
