Flash memory system and read method in flash memory system

摘要

Methods of operating nonvolatile memory devices include reading a first plurality of multi-bit nonvolatile memory cells in the nonvolatile memory device using a first plurality of read voltages to thereby generate first read data, and then rereading the first plurality of multi-bit nonvolatile memory cells using a second plurality of read voltages that differ, at least in part, from the first plurality of read voltages, to thereby generate second read data. An operation is then undertaken to perform first and second ECC decoding operations on the first and second read data, respectively, to thereby identify whether the first read data or the second read data more accurately reflects data stored in the first plurality of multi-bit nonvolatile memory cells during the reading and rereading.

主权项

1. A method of operating a nonvolatile memory device, comprising:
reading a first plurality of multi-bit nonvolatile memory cells in the nonvolatile memory device using a first plurality of read voltages to thereby generate first read data; rereading the first plurality of multi-bit nonvolatile memory cells using a second plurality of read voltages that differ, at least in part, from the first plurality of read voltages, to thereby generate second read data; and performing first and second ECC decoding operations on the first and second read data, respectively, to identify whether the first read data or the second read data more accurately reflects data stored in the first plurality of multi-bit nonvolatile memory cells during said reading and rereading, said performing first ECC decoding operations on the first read data being performed concurrently with said rereading; and performing soft decision at one of the read level at which the first data is read and the read level at which the second data is read, by comparing an ECC decoding result of the first data with an ECC decoding result of the second data.