Design of a novel reversible ALU using an enhanced carry look- ahead adder

Reversible logic is gaining significant consideration as the potential logic design style for implementation in modern nanotechnology and quantum computing with minimal impact on physical entropy. Recent advances in reversible logic allow schemes for computer architectures using improved quantum computer algorithms. Significant contributions have been made in the literature towards the design of reversible logic gate structures and arithmetic units, however, there are not many efforts directed towards the design of reversible ALUs. In this work, a novel programmable reversible logic gate is presented and verified, and its implementation in the design of a reversible Arithmetic Logic Unit is demonstrated. Then, reversible implementations of ripple-carry, carry-select and Kogge-Stone carry look-ahead adders are analyzed and compared. Next, implementations of the Kogge-Stone adder with sparsity-4, 8 and 16 were designed, verified and compared. The enhanced sparsity-4 Kogge-Stone adder with ripple-carry adders was selected as the best design, and its implemented in the design of a 32-bit arithmetic logic unit is demonstrated.