Patent ID: 8023323

Claim:
A method of driving a non-volatile memory device including a memory cell array of multi level cells, each multi level cell being configured to store one of a plurality of data states including a first data state and a second data state, according to a corresponding plurality of threshold voltage distributions including a first threshold voltage distribution and an adjacent second voltage distribution, the method comprising: designating a first portion of the memory cell array to include monitoring memory cells, and a second portion of the memory cell array to include programming units; performing a first preliminary read operation directed to a monitoring memory cell storing a target data state, wherein the first preliminary read operation discriminates between the first data state and the second data state using a first read voltage having a first voltage level between the first threshold voltage distribution and the second voltage distribution; comparing the target data state initially stored in the monitoring memory cell with a data state read from the monitoring memory cell during the first preliminary read operation; and setting a main read voltage for reading the memory cells of the programming units responsive to said comparing.