ELECTRICALLY WRITABLE NONVOLATILE SEMICONDUCTOR MEMORY

摘要

PROBLEM TO BE SOLVED: To minimize stress in cell transistor by extending the write set time when a predetermined repeating times of write and erase operation is exceeded. SOLUTION: Upon receiving an automatic write command, an automatic program control circuit 109 begins operation and an oscillator 110 generating a basic clock for controlling each circuit is started. A nonvolatile counter 113 counts up every time when automatic erase is executed. When the number of rewriting times stored in the nonvolatile counter 113 reaches a predetermined times, a decision is made that deterioration has progressed and a programming pulse width is set. A rewriting time is also set appropriately as required.