Design of Reversible Barrel Shift Register for Low Power VLSI

Sonia -

Abstract


Throughout the world, the numbers of hardware designer struggle for the reducing of power dissipation in VLSI systems. In case of designing of low power VLSI systems, the heat or energy is dissipated due to the irreversible or conventional design approach of digital VLSI system at the logical level. In this dissertation, a new approach of designing the digital systems at logical level is discussed. Reversible logics are the logic which does not dissipate the power, uses this concept in designing of digital VLSI system. The reversible logic has the promising applications in emerging computing paradigm such as quantum computing, quantum dot cellular automata, optical computing, etc. In reversible logic gates there is a unique one-to-one mapping between the inputs and outputs. To generate an useful gate function the reversible gates require some constant ancillary inputs called ancilla inputs. Also to maintain the reversibility of the circuits some additional unused outputs are required that are referred as the garbage outputs. The number of ancilla inputs, number of garbage outputs and quantum cost plays an important role in the evaluation of reversible circuits. Thus minimizing these parameters are important for designing an efficient reversible circuit. Barrel shifter is an integral component of many computing systems due to its useful property that it can shift and rotate multiple bits in a single cycle. The main contribution of this thesis is a set of design methodologies for the reversible realization of RBS where the designs are based on the Fredkin gate and the Feynman gate. The Fredkin gate can implement the 2:1 MUX with minimum quantum cost, minimum number of ancilla inputs and minimum number of garbage outputs and the Feynman gate can be used so as to avoid the fanout, as fanout is not allowed in reversible logic. The design methodologies considered in this work targets 1.) Reversible logical right shifter(RLRS), 2.) Reversible universal right shifter(RURS) that supports logical right shift, arithmetic right shift and the right rotate, 3.) Reversible bidirectional logical shifter(RBLS), 4.) Reversible bidirectional arithmetic and logical shifter(RBALS), 5) Reversible universal bidirectional shifter(RUBS) that supports bidirectional logical and arithmetic shift and rotate operations

Keywords


VLSI, Reversible Reversible Logic

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