ESTIMATION OF LEVEL-THRESHOLDS FOR MEMORY CELLS

摘要

Methods and apparatus are provided for determining level-thresholds for q-level memory cells. A group of the memory cells are read to obtain respective read signal components. The read signal components are processed in dependence on signal level to produce a signal level vector, comprising a series of elements, indicative of the distribution of read signal components in order of signal level. A plurality of possible sets of q−1 elements corresponding, respectively, to q−1 level-thresholds which partition the signal level vector into q segments, is then defined. The q−1 level-thresholds for the group of memory cells are then determined by selecting from said possible sets that set for which a predetermined difference function, dependent on differences in signal level for elements in each of said q segments for the set, has an optimum value.

主权项

1. A method for determining level-threshold of q-level memory cells, the method comprising:
reading a group of the memory cells to obtain respective read signal components; processing the read signal components in dependence on signal level to produce a signal level vector, comprising a series of elements, indicative of the distribution of read signal components in order of signal level; defining a plurality of possible sets of q−1 said elements corresponding, respectively, to q−1 level-thresholds which partition the signal level vector into q segments; and determining the q−1 level-thresholds for said group of memory cells by selecting from said possible sets that set for which a predetermined difference function, dependent on differences in signal level for elements in each of said q segments for the set, has an optimum value.