Combination-Encoding Content-Addressable Memory With High Content Density

Abstract

Recently, resistance switch-based content-addressable memory (RCAM) has been proposed as an alternative to the mainstream static random-access memory-based CAM because of its high integration potential and low static energy consumption. However, RCAM has a lower data density due to the use of a pair of resistance switches for a single bit of contents (0.5 bit/switch) than resistive random access memory (1 bit/switch). In this paper, we propose a new type of RCAM referred to as combination-encoding CAM (CECAM). In the N-CECAM, a single unit consists of N high and N low resistance state switches whose combination collectively represents binary contents, yielding a data density of approximately 0.85 bit/switch when N = 10, for instance. The key to the CECAM is the encoding of an n-bit search key as a 2N-digit key and its decoding. To this end, we propose a simple algorithm for encoding and decoding and its implementation in digital circuitry.