Design of Efficient Reversible BCD Adder–Subtractor Architecture and Its Optimization Using Carry Skip Logic

Abstract

In the present era, reversible logic designs play a very critical role in nanotechnology, low power complementary metal-oxide semiconductor (CMOS) designs, optical computing and, especially, in quantum computing. High power dissipation and leakage current in deep submicron technologies is a severe threat in applications created today. As a consequence, design of datapath elements in reversible logic has gained much importance. In this study, a novel design of binary coded decimal (BCD) adder/subtractor in reversible logic has been proposed. As a further optimization of the proposed reversible decimal design, carry skip (CSK) logic is used for reversible ripple carry adder stages. This reduces delay but at the expense of little hardware. The proposed BCD adder/subtractor and its optimized version are designed using structural VHDL and simulated using ModelSim 6.3f. Performance analysis reveals that the proposed BCD design demonstrates reductions in gate count, garbage outputs and constant inputs of 30.5%, 46% and 28%, respectively, and its optimized version exhibits 19.4%, 32.4% and 16% reductions in gate count, garbage outputs and constant inputs compared to the design in Ref. 14 [V. Rajmohan, V. Renganathan and M. Rajmohan, A novel reversible design of unified single digit BCD adder–subtractor, Int. J. Comput. Theor. Eng. 3 (2011) 697–700].