| 摘要 |
PURPOSE:To strengthen the security of a memory with large capacity so as to use it by forming two areas, a back memory area and a user memory area, in an EEPROM of an IC card and setting up a function accessing respective areas by an internal program. CONSTITUTION:The EEPROM 3 for storing IC card using data has addresses superposed to a built-in program area 4 in a microprocessor 2 and consists of two areas, the back memory area 6 for storing secret data and the user memory area 5 to be utilized by the microprocessor. Since memory apace other than an external memory accessable area 8 in the microprocessor 2 can be also accessed, the memory space to be practically utilized can be expanded and the large capacity memory in the IC card can be attained. Since the back memory area 6 can be accessed only by a signal formed by an internal program, the area 6 can not be accessed by an external normal instruction. Thereby, the memory 6 can be utilized for storing secret data or the like which must not be read out by an external instruction. |
