Patent ID: 8422291

Claim:
A storage device comprising: a storage unit configured to store data; an error controlling unit configured to correct an error of the data read out from the storage unit according to at least one read level; and a read level controlling unit including a filter and a modifier and configured to control the at least one read level when the error is uncorrectable, wherein the read level controlling unit is configured to measure a distribution of memory cells of the storage unit, configured to modify the measured distribution, configured to filter the modified distribution using the filter, and configured to reset the at least one read level based on the filtered distribution, the modifier is configured to modify a first region of a plurality of regions of the measured distribution in which a plurality of local minima exist where there is difficulty in setting the read level and configured to input values for at least a second region of the plurality of regions separate from the first region, and the filter is configured to filter the modified distribution to remove local minima in the modified distribution.