Structure And Algorithm Of Logical & Arithmetical Computing In Phase Change Memory By Bipolar Operations

Phase change memory,as the best alternative to current mainstream memory—FLASH,is also the most representative in next generation of non-volatile memories.It has extremely diverse and excellent characteristics: non-volatile storage,small size,long cycle life,fast read and write speed,low power consumption,low cost,multi-level storage function and so on.Multi-level storage,so called multi-state storage technology,is an effective approach to improving the utilization of phase change memory and the storage performance.The resistance drift phenomenon is one of the major obstacles to achieving multi-state storage.While modulated bi-polar pulses applied to a phase change memory cell can effectively restrain the resistance drift phenomenon,which intends to achieve more states of storage.The research of this paper is to realize computing operations in a phase change memory cell by using the multi-state storage technology.In this paper,a new equivalent circuit model is proposed based on the traditional HSPICE physical model of a phase change memory cell.In the model,the phase change memory cell is equivalent to a resistor network.The resistance of a phase change memory cell is equivalent to the charge amount on a capacitor in the circuit model.Charging and discharging processes of the capacitor can simulate the amorphization and crystallization processes respectively.This model can be used to intuitively analyze the change of the cell resistance during crystallization and amorphization.We also propose a structure that can carry out logical and algebraic operations based on phase change memory cells.We describe the realization method of binary logic operation and decimal addition and subtraction operations in detail.The simulation and analysis are carried out by using the equivalent model.And we verify the feasibility of these operations through some experiments.This paper also involves some expansion of multi-valued logic functions and algebra operations of other systems.