Patent ID: 7411837

Claim:
A method for operating an electrically writable and erasable memory cell, which has a channel region being operated in a first and a second direction, the memory cell characterized by at least one effective parameter, the method comprising: providing the memory cell, wherein: information is stored in the memory cell as one of at least three possible states, each of the at least three possible states comprises an associated magnitude and a difference, a first of the at least three possible states comprises a first magnitude and a first dfference; a second of the at least three possible states comprises the first magnitude and a second difference, the second difference less than the first difference; a third of the at least three possible states comprises a second magnitude and a third difference; an absolute value of each difference is less than an absolute value of a difference between the first magnitude and the second magnitude; each difference comprises a difference between the effective parameter in operation of the channel region in the first direction and the effective parameter in operation of the channel region in the second direction, each magnitude comprises an average of the effective parameter in operation of the channel region in the first direction and the effective parameter in operation of the channel region in the second direction; and retrieving the stored information from the memory cell.