Design of a reversible single precision floating point subtractor

Abstract

In recent years, Reversible logic has emerged as a major area of research due to its ability to reduce the power dissipation which is the main requirement in the low power digital circuit design. It has wide applications like low power CMOS design, Nano-technology, Digital signal processing, Communication, DNA computing and Optical computing. Floating-point operations are needed very frequently in nearly all computing disciplines, and studies have shown floating-point addition/subtraction to be the most used floating-point operation. However, few designs exist on efficient reversible BCD subtractors but no work on reversible floating point subtractor. In this paper, it is proposed to present an efficient reversible single precision floating-point subtractor. The proposed design requires reversible designs of an 8-bit and a 24-bit comparator unit, an 8-bit and a 24-bit subtractor, and a normalization unit. For normalization, a 24-bit Reversible Leading Zero Detector and a 24-bit reversible shift register is implemented to shift the mantissas. To realize a reversible 1-bit comparator, in this paper, two new 3x3 reversible gates are proposed The proposed reversible 1-bit comparator is better and optimized in terms of the number of reversible gates used, the number of transistor count and the number of garbage outputs. The proposed work is analysed in terms of number of reversible gates, garbage outputs, constant inputs and quantum costs. Using these modules, an efficient design of a reversible single precision floating point subtractor is proposed. Proposed circuits have been simulated using Modelsim and synthesized using Xilinx Virtex5vlx30tff665-3. The total on-chip power consumed by the proposed 32-bit reversible floating point subtractor is 0.410 W.

Reversible Gates: A Paradigm Shift in Computing

“…The gate count or gate cost (GC) of a circuit refers to the number of logic gates required to construct that circuit. It is a measure of the complexity and resource utilization of the circuit design [21]. The gate count is often used as an indirect measure of the cost of a circuit, as it correlates with factors such as manufacturing costs, power consumption, and performance.…”

“…We have categorized all the reversible gates present so far on the basis of the number of input-output vectors. [20] A⊕B B⊕C AB+BC+AC TS-3 [33] A B A⊕B⊕C RM [34] A⊕BC AB+AC AC+AB RG [35] A⊕B AB+BC+AC BC+A(B ⊕ C) RG1 [21] B AB+BC A⊕C G1 [36] B A B+AB A BC+AC+BC RG2 [21] A B ⊕C A ⊕ B A URLG [37] AB+BC+AC AB+BC+A C AB+B C+A C MPG [38] A A⊕B AB⊕C SAM [38] A AB⊕AC AC⊕AB R [34] A⊕B A C ⊕(AB) QCA1 [39] AB+BC+AC AB+BC+AC AB+BC+AC QCA2 [39] AB+BC+AC AB+BC+AC AB+BC+A C RQG [40] AB+BC+AC AB+BC+AC A⊕C Peres [41] A A⊕B AB⊕C URG [42] (A+B)⊕C B AB⊕C SSG [43] B⊕C A⊕B AB+BC+AC MNFT [44] (A⊕B)C⊕A A⊕B (A⊕B)C⊕A⊕C SRK [45] A…”

Low Power 32-Bit Floating Point Adder/Subtractor Design using 50nm CMOS VLSI Technology

“…8-bit, 16-bit, 32-bit, and 64-bit square-root CSLA (SQRT CSLA) have been designed and contrasted with the conventional SQRT CSLA design [16]. Reversible logic has developed as a noteworthy area of research because of its capacity to lessen the power dissipation which is the fundamental necessity in the low power design [14]. The layout design of the ripple carry adder is simple and it makes the calculation to be quicker [13].…”