| 摘要 |
<p>PURPOSE:To write writing data with one operation even when the data are to be written in the nonvolatile EEPROM under a written state and to improve the reliability of stored data by making only a transistor for storing bits to be necessary correspondingly to the writing data into an erased state at erasing operation time. CONSTITUTION:When writing data D0-D3 are 1010, and pre-writing storage contents are 1100, first, out of the transistors for storing of a memory cell part 102 (4 transistors with a transistor 111 as their representative), only some transistors in which the writing data D0-D3 correspond to 0 are erased by the automatic erasing function of the EEPROM. Namely, the transistors for storing the first and third bits are erased, and the transistors for storing the zero and second bits are held in their preceding states. Next, the data are written in the transistors for storing the zero and second bits by the writing operation of the EEPROM, and the transistors for storing the first and third bits are held in their erased states. The writing operation completes in this manner, and the expected value 1010 is outputted to outputs O0-O3 by the next reading out for confirmation.</p> |
