US Patent 7675772 Multilevel memory cell operation

One or more embodiments of the present disclosure provide methods, devices, and systems for operating non-volatile multilevel memory cells. One method embodiment includes programming a memory cell to one of a number of different threshold voltage (Vt) levels, each level corresponding to a program state. The method includes programming a reference cell to a Vt level at least as great as an uppermost Vt level of the number of different Vt levels, performing a read operation on the reference cell, and determining a number of read reference voltages used to determine a particular program state of the memory cell based on the read operation performed on the reference cell.