| 摘要 |
PROBLEM TO BE SOLVED: To avoid using a battery as an alternative battery of an external power supply even when power supply from the external power supply is stopped while writing predetermined information to a nonvolatile semiconductor storage device by using the external power supply as a power source.SOLUTION: A power supply selection unit 19 performs the following according to the amount of data of the predetermined information if power supply from an external power supply 13 is stopped while a writing control unit 15 is writing predetermined information to a nonvolatile semiconductor storage device 3 by using the power of the external power supply 13: selecting a storage circuit 9 as a power supply of the nonvolatile semiconductor storage device 3 and an IC chip 11 if the amount of data of the predetermined information is smaller than a predetermined first threshold value, and causing the writing control unit 15 to continue writing by using the power of the storage circuit 9; and selecting a battery 7 if the amount of data of the predetermined information is equal to or more than the first threshold value, and causing the writing control unit 15 to continue writing by using the power of a battery 7. |
