| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a nonvolatile multi-state memory which can operate with excellent performance even if a use period becomes a long period. <P>SOLUTION: In a circuit in which normal read-out and write-in for verifying or read-out during erasing are improved, read-out is performed for a series of threshold levels by a series of reference cells tracking closely to variation caused by a memory cell, adjusting, and corresponding. In some embodiment, each flash sector of the memory cell has a reference cell of itself for reading out a cell of a sector, the series of reference cells also exist for a whole memory chip operating as master reference. In the other embodiment, read-out is performed simultaneously for the series of threshold levels by a current mirror circuit of one to multi-state. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
