Non-volatile semiconductor memory and the testing method for the same

A system for determining the storage capability of each cell in a nonvolatile semiconductor memory device formed of an array of rows and columns of memory cells comprising:

• one or more reference memory cells;
• a reference voltage supply connected to said reference memory cells, wherein said reference voltage is greater than the threshold voltage and less than the storage voltage of said memory cells;
• a plurality of differential sense amplifiers;
• means for selectively coupling each column of memory cells to one input of a corresponding one of said plurality of differential sense amplifiers;
• and
• means for selectively coupling one or more of said reference memory cells to the other input of each of said plurality of differential sense amplifiers, wherein the output of the selected differential sense amplifier is related to the storage capability of a selected memory cell.