| 摘要 |
PURPOSE: To provide a non-volatile semiconductor memory with a high security function. CONSTITUTION: An inputted address is compared with an access inhibited address by a comparator 12 and when both the addresses are matched, a counter 14 counts the number of changed addresses inputted after the coincidence. This count number is compared with a previously set count number by a comparator 15 and when both the count numbers are matched, a ring oscillator 17 is oscillated. The number of cycles of this ring oscillator is compared with the previously set number of cycles by a comparator 18 and when both the numbers of cycles are matched, the inputted address is scrambled to output wrong data. When the inhibited address is accessed in the case of copying data, the wrong data are outputted after prescribed cycles, and a program is not normally operated by the copied data. Thus, practically illegal copy can be prevented. |
