Sk. Noor Mahammad

Bio: Sk. Noor Mahammad is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Computer science & Adder. The author has an hindex of 1, co-authored 1 publications receiving 73 citations.

Efficient Building Blocks for Reversible Sequential Circuit Design

Abstract: Reversible logic is gaining interest in the recent past due to its less heat dissipating characteristics. It has been proved that any Boolean function can be implemented using reversible gates. In this paper we propose a set of basic sequential elements that could be used for building large reversible sequential circuits leading to logic and garbage reduction by a factor of 2 to 6 when compared to existing reversible designs reported in the literature.

A Perspective of IP Lookup Approach Using Graphical Processing Unit (GPU)

Abstract: Due to increases in communication link capacity and growth of the Internet traffic, packet processing like IP address lookup and classification becomes a major concern in the network. The packet processing performed at Switch/Router does not cope up with the growing link speed. Since Graphics processing unit (GPU) has high parallelism and more flexibility for the programmers, it can be used for solving IP address lookup problem in the Switch/Router devices. This paper proposes a variant of trie based approach to find a solution for longest prefix match (LPM) problem using GPU. In this paper, IP address database is partitioned into a different table based on first k bits of IP address, then a variant of trie approach is proposed to find the next hop. The proposed lookup approach shows 64.46% and 94.32% improvement than binary trie and BST implementations.

Design of reversible sequential circuits optimizing quantum cost, delay, and garbage outputs

Abstract: Reversible logic has shown potential to have extensive applications in emerging technologies such as quantum computing, optical computing, quantum dot cellular automata as well as ultra low power VLSI circuits. Recently, several researchers have focused their efforts on the design and synthesis of efficient reversible logic circuits. In these works, the primary design focus has been on optimizing the number of reversible gates and the garbage outputs. The number of reversible gates is not a good metric of optimization as each reversible gate is of different type and computational complexity, and thus will have a different quantum cost and delay. The computational complexity of a reversible gate can be represented by its quantum cost. Further, delay constitutes an important metric, which has not been addressed in prior works on reversible sequential circuits as a design metric to be optimized. In this work, we present novel designs of reversible sequential circuits that are optimized in terms of quantum cost, delay and the garbage outputs. The optimized designs of several reversible sequential circuits are presented including the D Latch, the JK latch, the T latch and the SR latch, and their corresponding reversible master-slave flip-flop designs. The proposed master-slave flip-flop designs have the special property that they don't require the inversion of the clock for use in the slave latch. Further, we introduce a novel strategy of cascading a Fredkin gate at the outputs of a reversible latch to realize the designs of the Fredkin gate based asynchronous set/reset D latch and the master-slave D flip-flop. Finally, as an example of complex reversible sequential circuits, the reversible logic design of the universal shift register is introduced. The proposed reversible sequential designs were verified through simulations using Verilog HDL and simulation results are presented.

Constructing Online Testable Circuits Using Reversible Logic

Abstract: With the advent of nanometer technology, circuits are more prone to transient faults that can occur during its operation. Of the different types of transient faults reported in the literature, the single-event upset (SEU) is prominent. Traditional techniques such as triple-modular redundancy (TMR) consume large area and power. Reversible logic has been gaining interest in the recent past due to its less heat dissipation characteristics. This paper proposes the following: 1) a novel universal reversible logic gate (URG) and a set of basic sequential elements that could be used for building reversible sequential circuits, with 25% less garbage than the best reported in the literature; (2) a reversible gate that can mimic the functionality of a lookup table (LUT) that can be used to construct a reversible field-programmable gate array (FPGA); and (3) automatic conversion of any given reversible circuit into an online testable circuit that can detect online any single-bit errors, including soft errors in the logic blocks, using theoretically proved minimum garbage, which is significantly lesser than the best reported in the literature.

Design of efficient reversible logic-based binary and BCD adder circuits

Abstract: Reversible logic is gaining significance in the context of emerging technologies such as quantum computing since reversible circuits do not lose information during computation and there is one-to-one mapping between the inputs and outputs. In this work, we present a class of new designs for reversible binary and BCD adder circuits. The proposed designs are primarily optimized for the number of ancilla inputs and the number of garbage outputs and are designed for possible best values for the quantum cost and delay. In reversible circuits, in addition to the primary inputs, some constant input bits are used to realize different logic functions which are referred to as ancilla inputs and are overheads that need to be reduced. Further, the garbage outputs which do not contribute to any useful computations but are needed to maintain reversibility are also overheads that need to be reduced in reversible designs. First, we propose two new designs for the reversible ripple carry adder: (i) one with no input carry c0 and no ancilla input bits, and (ii) one with input carry c0 and no ancilla input bits. The proposed reversible ripple carry adder designs with no ancilla input bits have less quantum cost and logic depth (delay) compared to their existing counterparts in the literature. In these designs, the quantum cost and delay are reduced by deriving designs based on the reversible Peres gate and the TR gate. Next, four new designs for the reversible BCD adder are presented based on the following two approaches: (i) the addition is performed in binary mode and correction is applied to convert to BCD when required through detection and correction, and (ii) the addition is performed in binary mode and the result is always converted using a binary to BCD converter. The proposed reversible binary and BCD adders can be applied in a wide variety of digital signal processing applications and constitute important design components of reversible computing.

Design of Reversible Latches Optimized for Quantum Cost, Delay and Garbage Outputs

Abstract: Reversible logic has extensive applications in emerging nanotechnologies, such as quantum computing, optical computing, ultra low power VLSI and quantum dot cellular automata. In the existing literature, designs of reversible sequential circuits are presented that are optimized for the number of reversible gates and the garbage outputs. The optimization of the number of reversible gates is not sufficient since each reversible gate is of different computational complexity, and thus will have a different quantum cost and delay. While the computational complexity of a reversible gate can be measured by its quantum cost, the delay of a reversible gate is another parameter that can be optimized during the design of a reversible sequential circuit. In this work, we present novel designs of reversible latches that are optimized in terms of quantum cost, delay and the garbage outputs. The optimized designs of reversible latches presented in this work are the D Latch, JK latch, T latch and SR latch.

Mapping of Subtractor and Adder-Subtractor Circuits on Reversible Quantum Gates

Abstract: Reversible arithmetic units such as adders, subtractors and comparators form the essential components of any hardware implementation of quantum algorithms such as Shor's factoring algorithm. Further, the synthesis methods proposed in the existing literature for reversible circuits target combinational and sequential circuits in general and are not suitable for synthesis of reversible arithmetic units. In this paper, we present several design methodologies for reversible subtractor and reversible adder-subtractor circuits, and a framework for synthesizing reversible arithmetic circuits. Three different design methodologies are proposed for the design of reversible ripple borrow subtractor that vary in terms of optimization of metrics such as ancilla inputs, garbage outputs, quantum cost and delay. The first approach follows the traditional ripple carry approach while the other two use the properties that the subtraction operation can be defined as $$a-b$$ = $$\overline{\bar{a}+b}$$ and $$a-b$$ = $${a+\bar{b}+1}$$, respectively. Next, we derive methodologies adapting the subtractor to also perform addition as selected with a control signal. Finally, a new synthesis framework for automatic generation of reversible arithmetic circuits optimizing the metrics of ancilla inputs, garbage outputs, quantum cost and the delay is presented that integrates the various methodologies described in our work.