Patent ID: 9594615
Date: 2017-03-14
CPC Classifications: G06F,G11C

Claim:
1. A method for data storage, comprising: in a memory device comprising multiple memory cells that store data in analog values, defining a given setting of one or more read thresholds; dividing a range of the analog values into multiple zones depending on the read thresholds, and assigning reliability levels to hard bit decisions associated with the respective zones; performing a hard read operation that reads the analog values from a group of the memory cells and produces hard bit decisions regarding positions of the read analog values relative to the read thresholds of the given setting of the read thresholds; identifying erroneous hard decisions in the data that was read in the hard read operation using the given setting of the read thresholds, and performing a classification of the erroneous hard decisions into at least first and second different hard-error types, depending on the zones in which the analog values fall; and determining for the group of the memory cells, based on evaluated numbers of the erroneous hard decisions of the first and second hard-error types, a memory quality metric that depends on the different reliability levels assigned to the erroneous hard decisions of the first and second hard-error types.