Realizing Reversible Computing in QCA Framework Resulting in Efficient Design of Testable ALU

Abstract

Reversible logic is emerging as a prospective logic design style for implementing ultra-low-power VLSI circuits. It promises low-power consuming circuits by nullifying the energy dissipation in irreversible logic. On the other hand, as a potential alternative to CMOS technology, Quantum-dot Cellular Automata (QCA) promises energy efficient digital design with high device density and high computing speed. The integration of reversible logic in QCA circuit is expected to be effective in addressing the issue of energy dissipation at nano scale regime. This work targets the design of reversible ALU (arithmetic logic unit) in QCA framework and proposes a new “Reversible QCA” (RQCA). The primary design focus is on optimizing the number of reversible gates, quantum cost and the garbage outputs that are the most important hindrances in realizing reversible logic. Besides optimization, the fault coverage capability of RQCA under missing/additional cell deposition defects is analysed. The scope of reversible logic is further outstretched by introducing a novel DFT (design for testability) architecture around the reversible ALU that reduces testing overhead. The performance of proposed ALU is evaluated, subjected to different faults, and is established to be more effective than the existing ALU.