SEMICONDUCTOR MEMORY DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a semiconductor memory device in which data written in a non-volatile memory once is surely protected and a security function of EEPROM data is high. SOLUTION: This device is constituted of user memory region 10 in which a user can write arbitrary data, and a write information storing memory region 11 in which data write presence absence information performed for the user memory region 10 is stored. Also, password authentication is used, as used clock frequency is made variable, and password authentication is performed by a varied clock used for the pass word authentication.