Design of a Reversible Binary Coded Decimal Adder by Using Reversible 4-bit Parallel Adder

Babu, H. M. H. Chowdhury, A.R, “Design of a reversible binary coded decimal adder by using reversible 4-bit parallel adder,” 18th International Conference on VLSI Design, pp. 255 - 260, 2005.

Advisor : Dr . Shu-Chung Yi Author : Shi-Xun Chang

Outline

1 . Introduction2 . Synthesis algorithm of the propose circuit3 . Full-design of the propose BCD adder4 . Conclusions

Introduction

This paper has proposed a design technique for the reversible circuit of Binary Coded Decimal adder . The proposed circuit has the ability to add two 4-bits binary variables and it transforms the addition into the appropriate BCD number with efficient error correcting modules where the operations are reversible .

Synthesis algorithm of the propose circuit

Construct a reversible full-adder circuit efficiently so that the circuit requires very few numbers of gates and generates small number of garbage outputs.

Synthesis algorithm of the propose circuit

Construct a reversible 4 bits parallel adder by cascading four copies of reversible full-adder circuits .

Synthesis algorithm of the propose circuit

Construct necessary combinational logic to control overflow of the result of addition by selecting appropriate reversible gates .

Synthesis algorithm of the propose circuit

Apply two 4 bits operands (A 3A 2A 1A 0 and B 3B 2B 1B 0) into the first 4 bits reversible adder and generate the initial sum (S 3S 2S 1S 0) and carry C 4 .

Synthesis algorithm of the propose circuit

Apply the result into the combinational logic for error correction .

Synthesis algorithm of the propose circuit

Apply the initial sum (S 3S 2S 1S 0) into the first four pins of the second reversible 4-bits parallel adder and error correcting code into the last four pins to get the final addition .

Full-design of the propose BCD adder

Conclusions

The proposed BCD adder circuit can further be used in a large reversible system as a module of reversible logic .In future , we have the plan to construct large reversible system that executes more than one reversible operations concurrently .