Patent ID: 7924613
Filing Date: 2011-04-12
Classification: G11C

Abstract:
1. A method for data storage, comprising: storing first data in analog memory cells using a first programming operation, which writes to the memory cells respective analog values representing respective bit values of the first data; and storing in the analog memory cells second data in addition to the first data using a second programming operation, which modifies the respective analog values of the memory cells so as to represent bit value combinations of the first and second data, wherein the first and second programming operations are defined such that, at all times during the second programming operation, the analog value of each memory cell remains unambiguously indicative of the respective bit value of the first data stored in that memory cell, wherein the first and second programming operations are defined such that the analog values that are potentially reached during the second programming operation by the memory cells that store a first bit value of the first data are contained in a first range, and the analog values that are potentially reached during the second programming operation by the memory cells that store a second bit value of the first data, different from the first bit value, are contained in a second range that does not overlap the first range, and comprising, following an interruption in the second programming operation, reconstructing the first data by reading the analog values from the memory cells using a read threshold positioned between the first and second ranges.