Design of Novel Reversible Carry Look-Ahead BCD Subtractor

1. Design of Novel Reversible Carry Look-Ahead BCD Subtractor Thapliyal, Himanshu Gupta, Sumedha K, “Design of Novel Reversible Carry Look-Ahead BCD Subtractor”. ICIT '06. 9th International Conference on Information Technology, pp . 253 – 258 , Dec. 2006. Advisor : Dr . Shu-Chung Yi Author : Shi-Xun Chang

2. Outline 1 . Introduction 2 . BCD Subtractor 3 . Carry Look Ahead Adder 4 . Reversible Carry Look-Ahead BCD Subtractor 5 . Conclusions

3. Introduction The decimal arithmetic is receiving significant attention as the financial，commercial，and internet-based application can not tolerate errors generated by conversion between decimal and binary formats。

4. BCD Subtractor In the BCD subtraction，nine’s complement of the subtrahend is added to the minuend 。In BCD arithmetic ，instead of subtracting the number from nine ，the Nine’s complement of a number is determined by adding 1010 (decimal 10) to the one’s complement of the number 。

5. BCD Subtractor

6. Carry Look Ahead Adder

7. Reversible Carry Look-Ahead BCD Subtractor

8. Conclusions The focus of this paper is the IEEE 754r considering decimal arithmetic and the promising paradigm of reversible logic 。Thus，this paper proposes novel carry look-ahead BCD subtractor along with its optimal reversible logic implementation 。