High speed, nonvolatile, electrically erasable memory cell and system

Abstract

A method for encoding binary data into an electrically erasable memory. The memory includes a matrix of memory cells formed as a plurality of rows (X write lines/X sense lines/source lines) and columns (Y sense lines) with each cell including a floating gate field effect PMOS transistor and an NPN bipolar transistor. The method includes applying an erase voltage, e.g. +20 volts, to each of the Y sense lines while maintaining each of the X sense lines at this erase voltage and each of the X write lines at ground and applying the erase voltage to each of the source lines such that each of the PMOS transistors assumes a relatively negative threshold state. The method includes applying a write voltage e.g., +20 volts, to selected X write lines while maintaining unselected X write and selected Y sense lines at ground and unselected Y sense lines at an inhibit voltage e.g., +10 volts, which is less than the write voltage, and maintaining each of the X sense lines at an intermediate voltage e.g., +5 volts, such that the PMOS transistors of memory cells located at the intersections of the selected X write lines and the selected Y sense lines assume a relatively positive threshold state.