| 摘要 |
The invention relates to electrically programmable memories, and in particular memories known by the acronyms "EPROM", "EEPROM", "FLASH-EEPROM".
<??>To increase the information storage capacity of a memory, it is proposed to define at least three (instead of two) segments of current which issues from a cell to which reading voltages are applied; these segments correspond to n possible programming states for the cell. Comparators (COMP1, COMP2, COMP3) define an item of information stored for example in 2-bit form on outputs S1, S2. However, to ensure security when reading, despite the uncertainties of programming, the cell is tested with the aid of additional comparators (COMP1A, COMP2A, COMP3A) and if the measured cell current for a specified programming level, out of n, is too close to the current threshold defining the programming threshold at this level, an operation of supplementary programming of the cell is triggered.
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