| 摘要 |
<p>PURPOSE:To set the contour of a data block by an EPROM itself by setting the threshold value of a memory cell to three values such as high, middle and low, expressing a data with the two values, expressing the index of the data block with the remaining one value and reading these data and index. CONSTITUTION:The storing state of the non-volatile memory cell is set to the three values of '0', '1' and '2'. Among those values, the two values such as '0' and '1', for example, are used for the data and the remaining one value such as '2', for example, is used for the index of the data block. In a normal read mode, the stored data of the memory cell storing the two values for data are read out and in the read mode of an index bit, the stored data of the memory cell storing the one value for index are read out. Namely, in reading with a threshold value L1, the stored data of the memory cell turned on at this time is '0', for example, and the stored data of the cell to be turned off is '1' or '2'. In reading with a threshold value L2, the stored data of the cell to be turned at such a time is '0' or '1' (data) and the stored data of the cell to be turned off is '2' (index). Thus, the index can be attached to the data block.</p> |
