Design of Novel Reversible Carry Look-Ahead BCD Subtractor

IEEE 754r is the ongoing revision to the IEEE 754 floating point standard. A major enhancement to the standard is the addition of decimal format, thus the design of BCD arithmetic units is likely to get significant attention. Firstly, this paper introduces a novel carry look-ahead BCD adder and then builds a novel carry look-ahead BCD subtracter based on it. Secondly, it introduces the reversible logic implementation of the proposed carry look-ahead BCD subtracter. We have tried to design the reversible logic implementation of the BCD Subtracter optimal in terms of number of reversible gates used and garbage outputs produced. Thus, the proposed work will be of significant value as the technologies mature.