| 摘要 |
<p>PURPOSE:To prevent the change of data due to an erroneous writing after a data writing by prohibiting a data writing action for a memory cell in a memory cell array based on the holding data of a cell for a data writable flag. CONSTITUTION:After the data writing for all the cells is completed, the writing to a PROM cell 12 for a flag is executed by inputting a certain specific signal with a user. After this, since a transistor 10 is made into an ON state by the data from the PROM cell 12 even when, for example, a potential is turned into a writing potential Vpp by an erroneous action, the writing potential Vpp is short-circuited to a ground potential Vss. Consequently, since the writing potential Vpp is not supplied to a transistor 9, which is a main body memory cell, a rewriting is prohibited. Thus, an erroneous data writing due to various causes can be prevented.</p> |
