Efficient Re-read Operations in Analog Memory Cell Arrays

摘要

A method for data storage includes storing data, which is encoded with an Error Correction Code (ECC), in a group of analog memory cells by writing respective first storage values to the memory cells in the group. After storing the data, respective second storage values are read from the memory cells in the group, and the read second storage values are processed so as to decode the ECC. Responsively to a failure in decoding the ECC, one or more of the second storage values that potentially caused the failure are identified as suspect storage values. Respective third storage values are re-read from a subset of the memory cells that includes the memory cells holding the suspect storage values. The ECC is re-decoded using the third storage values so as to reconstruct the stored data.

主权项

1. An apparatus, comprising:
a plurality of non-volatile memory cells configured to store data encoded with an Error Correction Code (ECC); and circuitry coupled to the plurality of non-volatile memory cells, wherein the circuitry is configured to:
read storage values from the plurality of non-volatile memory cells using a first read threshold to generate first values;decode the ECC dependent upon the first value;re-read, responsive to a failure of the decoding of the ECC, the storage values from the plurality of non-volatile memory cells, using a second read threshold and a third read threshold to generate second values and third values, respectively, wherein the second read threshold is less than the first read threshold, and wherein the third read threshold is greater than the first read threshold;identify at least one storage value that potentially caused the failure of the decoding of the ECC dependent upon the second and third values; andre-read, using a fourth read threshold, the at least one storage value from only a subset of the plurality of non-volatile memory cells including non-volatile memory cells storing the at least one storage value to generate fourth values, wherein a number of cells in the subset of the plurality of non-volatile memory cells is less than a number of cells in the plurality of non-volatile memory cells.