Optoelectronic content addressable memory-based modified signed digit arithmetic

Abstract

The modified signed digit (MSD) number system offers inherent low interdigit dependence for arithmetic processing. Recently, using both optical logic and memory based approaches, various optical MSD arithmetic schemes were proposed. For the logic based optical MSD arithmetic, an existing approach implements a three-stage processing algorithm with either a symbolic substitution processor or some binary logic elements, such as bistable etalons. Because of the use of multiple processing stages, the required computing energy and its speed is sacrificed. The optical memory based approach, on the other hand, utilizes a single-stage content addressable memory (CAM) for a fast MSD arithmetic. However, the existing holographic CAM is difficult to implement. In this talk, a new nonholographic CAM scheme for a single-stage MSD addition processing is proposed and demonstrated. A position encoded 18 × 56 pixel CAM mask is used in an angularly multiplexed geometry for a parallel CAM matching operation. Electronic logic inverters are used as the output devices.