FLASH MEMORY, FLASH MEMORY SYSTEM AND OPERATING METHOD OF THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a flash memory, a flash memory system and an operating method of the same.SOLUTION: A method of operating a flash memory comprises: counting the number of memory cells having threshold voltages included in a first reference threshold voltage range A defined by a first reference read voltage RRV 1 for discriminating between a first pair of threshold voltage distributions S1, S2 adjacently located and by a first search read voltage SRV 11 having a first voltage difference from the first reference read voltage, and counting the number of memory cells having threshold voltages included in a second reference threshold voltage range B defined by the first reference read voltage RRV 1 and by a second search read voltage SRV 12 having a second voltage difference from the first reference read voltage RRV 1; and setting a first optimal read voltage ORV 1 on the basis of the difference between the counted numbers of the memory cells having the threshold voltages included in the first reference threshold voltage range A and in the second reference threshold voltage range B.