Patent ID: 7489543
Filing Date: 2009-02-10
Classification: G11C

Abstract:
1. A method for programming a memory cell, comprising: if it is desired to alter a first digit of a data value of the memory cell, shifting the memory cell from a first data state to a second data state; and if it is desired to alter a second digit of the data value of the memory cell, shifting the memory cell to a third data state if the memory cell is in the first data state and shifting the memory cell to a fourth data state if the memory cell is in the second data state; wherein each data state is represented by a range of threshold voltages for the memory cell; wherein each threshold voltage of the fourth data state is greater than any threshold voltage of the third data state; wherein each threshold voltage of the third data state is greater than any threshold voltage of the second data state; and wherein each threshold voltage of the second data state is greater than any threshold voltage of the first data state.