| 摘要 |
PROBLEM TO BE SOLVED: To protect the content of a rewritable memory with an inexpensive constitution, by comparing the output voltage generated in a power circuit with a reference voltage and restricting the writing/reading of data into/from a memory when the output volage is lower than a prescribed value. SOLUTION: A comparator 35 inputs the output of the power circuit 27 and ground voltage used as reference voltage and outputs the compared result to a microprocessor 24. The output of the comparator 35 is set so that it changes when the difference of reference voltage and power voltage becomes under 3.0V, for example. When power voltage drops to 3.0V be cause an interval between a main body device 10 and an IC card 20 is extended, the output of the comparator 35 changes and a denial response is returned against a write request from the main body device 10. When write inhibition voltage is set to that by which the writing of data sent till the return of the denial response can be terminated while the power voltage of the IC card 20 attenuates to write guarantee voltage, erroneous data is prevented from being kept in the memory. |
