| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve reliability in reading of nonvolatile semiconductor memory. <P>SOLUTION: A controller includes: a program interface 102 for setting a first threshold voltage level depending on write information in a memory cell; a generation unit 106 configured to aggregate comparison results between second threshold voltage levels held in the memory cells and predetermined third threshold voltage levels, and generate a histogram of the second threshold voltage levels; an estimation unit 107 configured to estimate statistical parameter of a distribution of the second threshold voltage levels with respect to a first threshold voltage level, based on the histogram; and a determination unit 108 configured to determine a fifth threshold voltage level defining a boundary of a fourth threshold voltage level indicating a read result of the memory cells from the third threshold voltage levels, based on the statistical parameter in such a manner that mutual information amount between the first threshold voltage level and the fourth threshold voltage level becomes maximum. <P>COPYRIGHT: (C)2011,JPO&INPIT |
