Designing QCA Delay-Insensitive Serial Adder

Tabrizizadeh, E.; Mohaqeq, Hamid Reza; Vafaei, Abbas

doi:10.1109/icetet.2008.65

Cited by 6 publications

(5 citation statements)

References 25 publications

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“…As a matter of fact, using this layout the length of all the wires from every input to every output in terms of clock cycles is the same. Consequently signals are perfectly synchronized without the need of asynchronous protocols like widely discussed in [23] [25] [39] [21].…”

Section: Nml Background and Circuits Organizationmentioning

confidence: 99%

“…The first issue is related to technological features that have a few consequences: i) circuits are intrinsically pipelined, ii) the pipeline depth is dictated by technology, and iii) the delay of a signal is counted in terms of number of clock cycles and depends on the circuit layout. This aspect has been baptized "layout=timing" [19], it is well known and several works and discussions on careful circuit layout have been carried on and circuit level solutions have been deeply analyzed [20] [21] [22] [23] [24] [25].…”

Section: Introductionmentioning

confidence: 99%

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Feedbacks in QCA: A Quantitative Approach

Vacca

Wang

Graziano

et al. 2015

IEEE Trans. VLSI Syst.

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In the post-CMOS scenario a primary role is played by Quantum dot Cellular Automata (QCA) technology. Irrespective of the specific implementation principle (e.g. either molecular, magnetic or semi-conductive in current scenario) the intrinsic deep-level pipelined behavior is the dominant issue. It has important consequences on circuit design and performance especially in presence of feedbacks in sequential circuits. Though partially already addressed in literature, these consequences still must be fully understood and solutions thoroughly approached in order to allow this technology any further advancement. This work conducts an exhaustive analysis of the effects and the consequences derived by the presence of loops in QCA circuits. For each problem arisen a solution is presented. The analysis is performed using as test architecture a complex systolic array circuit for biosequences analysis (Smith-Waterman algorithm) which represents one of the most promising application for QCA technology. The circuit is based on NanoMagnetic Logic as QCA implementation, is designed down to the layout level considering technological constraints and experimentally validated structures, counts up to approximately 2.3Ml nanomagnets, is described and simulated with HDL language using as a testbench realistic protein alignment sequences. The results here presented constitute a fundamental advancement in the emerging technologies field, since, 1) they are based on a quantitative approach relying on a realistic and complex circuit involving a large variety of QCA blocks, 2) they strictly are reckoned starting from current technological limits without relying on unrealistic assumptions, 3) they provide general rules to design complex sequential circuits with intrinsically pipelined technologies, like QCA, 4) they prove with a real application benchmark how to maximize the circuits performance.

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Section: Nml Background and Circuits Organizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Feedbacks in QCA: A Quantitative Approach

Vacca

Wang

Graziano

et al. 2015

IEEE Trans. VLSI Syst.

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“…Other asynchronous implementations could fit this problem. We started this analysis from NCL considering that it was proposed in [7] as a promising solution, but that its benefits and aftereffects have not been established jet in terms of realistic performance. In NCL every signal is coded using two bits, that can assume two different values: DATA = 01 or 10 (that stand for a Boolean '0' and '1') and NULL = 00, while 11 is forbidden.…”

Section: Magnetic Qca Clock Systemmentioning

confidence: 99%

“…The number and the position of logic gates is constrained like in the standard digital circuits, and the same principles and automatic algorithms can then be adopted. A general NCL implementation applied to QCA circuits is proposed in [7], while a specific solution for magnetic circuits is presented in our work in [4] [5] and is the starting point for this work. The proposed system is thus a GALS one: Globally Asynchronous (the handshake protocol to allow information propagation) and Locally Synchronous (the clock system to enable information propagation).…”

Section: Introductionmentioning

confidence: 99%

Asynchrony in Quantum-Dot Cellular Automata Nanocomputation: Elixir or Poison?

Graziano

Vacca

Blua

et al. 2011

IEEE Des. Test. Comput.

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Quantum dot Cellular Automata (QCA) technology is a possible CMOS substitute. It requires a clock-like signal to assure information propagation. This likens a QCA circuit to a fully pipelined architecture, where pipeline depth is layout dependent. Only asynchronous organization of architectural blocks enables the realization of complex circuits. The use of Null Convention Logic (NCL) is one among the proposed solutions. However there is no certainty that the balance between positive and negative aspects of this logic will be favorable for QCA. We analyze pros and cons of NCL and Boolean logic circuits applied to QCA, using a VHDL behavioral model of QCA gates, in terms of speed, latency, power and area. We point out a critical problem related to feedback signals: Clearing it is mandatory in order to implement complex QCA circuits. Finally we propose a hybrid logic solution which is the best compromise between performance and problem solutions, and we give a sound answer to this paper title question.

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“…Tabrizizadeh et al [30] 2008 A new QCA serial adder has been designed which is delayinsensitive QCA. The registers are used to control the flow of information within the circuit modules.…”

Section: Evolution Of Qca Addersmentioning

confidence: 99%