Read measurements of resistive memory cells

摘要

Methods and apparatus are provided for read measurement of resistive memory cells 11 having two or more programmable cell-states. In a voltage-mode read operation, at least one initial voltage is applied 13 to each cell 11 and a measurement, indicative of cell current 14 due to the initial voltage, is made. A read voltage is then determined for the cell in dependence on the initial measurement. The read voltage is applied to the cell 11, and a read measurement, indicative of cell current 14 due to the read voltage, is made. A cell-state metric dependent on the read measurement is then output. For example, the read measurement may be output as a cell-state metric. The read voltages for cells are determined in such a manner that the cell-state metric exhibits a desired property, e.g. provides an enhanced programming window (figure 5,6) and/or a desired programming curve shape. A current-mode read operation, involving application of currents to cells 11 and measuring resulting voltages can be similarly performed.