Quantum-dot Cellular Automata Serial Adder Design Exploiting Null Convention Logic

Although QCA (Quantum-dot Cellular Automata) has been introduced as a new kind of technology for over a decade, it still continued to be so and its merits and flaws were yet under study for future practical use. One of the problems of this technology has been the dependency of its circuit timing to its layout. An asynchronous design methodology for QCA has been offered to solve this problem. The proposed methodology uses NCL (Null Convention Logic) to approach this issue. Since asynchronous registers played an important role in NCL methodology, to ease the problem this work was aimed to design asynchronous registers and employed them to construct a delay insensitive serial adder. By using the results obtained so far an approximate formula evaluate the required cell number and hence space is proposed in this paper which can be used for estimation proposes in the future QCA system design.