Patent ID: 8570814

Claim:
A non-volatile memory apparatus, comprising: an electrically-alterable non-volatile memory cell having more than two predetermined memory states; a programming signal source which applies a programming signal to said memory cell; control circuitry which generates a plurality of programming reference parameters and selects among said plurality of programming reference parameters in accordance with information indicating a memory state to which said memory cell is to be programmed, each programming reference parameter corresponding to a different memory state of the memory cell, and said control circuitry controlling the application of said programming signal to said memory cell based on the selected programming reference parameter; and read circuitry which reads the state of the memory cell by comparing a parameter corresponding to the state of the memory cell with a plurality of read reference parameters having values that are different from values of said programming reference parameters, and wherein, for each read reference parameter and a corresponding programming reference parameter, the value of one of the read reference parameter and the programming reference parameter is shifted from and dependent upon the value of the other.