OPERATIING METHOD OF NONVOLATILE MEMORY SYSTEM

摘要

The present invention relates to a method for operating a nonvolatile memory system, to enhance the reliability of detecting an optimal read voltage. According to one embodiment of the present invention, the method comprises the following steps: detecting the number of on-cells of memory cells on the basis of a start sampling voltage; comparing the detected number of on-cells with a reference value; setting sampling voltages on the basis of the comparison result; performing a sampling operation on the memory cells on the basis of the sampling voltages; and detecting an optimal read voltage to discriminate any one of program states on the basis of the result of the sampling operation.