| 摘要 |
<p>PURPOSE:To surely protect a data by a method wherein the number of rewrite operations is limited at one part of an electrically erasable and programmable read-only memory element (EEPROM) and the data is fixed for a rewrite operation after the number of rewrite operations. CONSTITUTION:A memory cell array 1 composed of an EEPROM is constituted of a rewrite region 11 where a data can be rewritten and of a region 12 where the number of rewrite operations is limited. That is to say, before the data is written to the memory limitation region 12, a set value of a counter 9 until the data is fixed is serially input in advance from an external terminal; the data can be rewritten up to the number of rewrite operations of the set value; when the number is exceeded, the data can be fixed completely. Thereby, it is possible to protect them from an erroneous write operation.</p> |
