| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a nonvolatile semiconductor storage for calculating the number of write times to a plurality of memory cells speedily. <P>SOLUTION: A memory cell array 1 has a plurality of memory cells for storing a plurality of bits in one memory cell. A sense amplifier unit 3a detects data read from a selected memory cell MC of the memory cell array. At the time of a write verify operation for verifying write data, when a threshold voltage of the memory cell exceeds a preset verification checkpoint, the data control unit 3b converts write data to the memory cell to count data indicating the remaining number of write voltage application times, inverts only one bit of the count data each time a write voltage application operation is performed, and changes a definition of the count data to perform a subtraction operation. <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
