1. A system for determining resistance states at crossbar junctions of a crossbar array, the system comprising: one or more sense amplifiers ( 512 - 514 ) connected to column wires of the crossbar array; a reference row wire ( 516 ) connected to each sense amp; and a wire driver ( 518 ) connected to the reference row wire and configured to drive the reference row wire, wherein the sense amplifiers are configured so that when a selected row wire of the crossbar array is driven by a sense voltage, the column wires are held at approximately zero volts and pass currents through the column wires and sense amplifiers to the reference row wire so that resistive voltage losses along the reference row wire substantially mirror the resistive voltage losses along the selected row wire allowing the sense amplifiers to determine the crossbar junction resistance states.