Abstract: In this paper, we made an analysis on the logic operations involved in conventional carry select adder (CSLA) and CSLA based on binary to excess-1 converter (CSLA-BEC) to study the data-dependency, and to find redundant logic operations. We have eliminated all the redundant logic operations of conventional CSLA, and proposed a logic formulation for CSLA. In the proposed scheme, the carry-select operation is scheduled before the calculation of final-sum, which is different from the conventional approach. A CSLA based on the proposed scheme generate n-bit carry-words corresponding to input-carry ’0’ and ’1’, where n is the input bit-width. These carry words follow a specific bit-pattern which can be used for logic optimization of carry-select unit. Fixed input bits of carry generator unit also can be used for logic optimization. Based on this, an optimized design for carry-select unit and carry generator unit are obtained. Using these optimized logic units, an efficient design is obtained for CSLA. Due to small carry-output delay, the proposed CSLA design is a good candidate for SQRT adder.

Keywords: Adder, BEC, Low power design, CSLA

| DOI: 10.17148/IARJSET.2021.8543