| 摘要 |
PURPOSE:To back up a volatile memory having large capacity with a memory back-up system by loading again the data which is saved to a nonvolatile memory when a power supply is applied again after a prescribed period of time from the break of the power supply. CONSTITUTION:When a slave terminal 1 is set into a break sequence of a power supply, a terminal main body 11 transmits the memory data of a volatile memory 13 to a master unit 2 through a loop transmission line 3 to shunt and store it to the corresponding area of a nonvolatile memory 23. At the same time, the power supply breaking time point is stored to a register 16. When the power supply of the terminal 1 is applied again, the main body 11 calculates the time elapsed from the breaking time point of the power supply and compares it with the conducting lifetime of a battery 14. If the former time is shorter than the latter time, the contents of the memory 13 are used as they are. While the data saved to the memory 23 is loaded again if the former time is longer than the latter time. |
