A basic circuit for asynchronous superconductive logic using RSFQ gates

This paper presents a basic circuit concept for pulse-driven asynchronous circuits using superconducting rapid single-flux-quantum (RSFQ) logic gates. Today's computer systems perform using a synchronous clock distributed over the whole system. The distribution of the clock signal becomes more difficult as the clock frequency increases because the wavelength of the clock signal becomes shorter than the system size. One way to solve this problem is to use asynchronous circuits in which all circuits perform their functions only under the law of cause and effect. We propose an implementation of the basic asynchronous circuit performing OR/AND logic operations between SFQ pulses. The operations are confirmed by SPICE simulation. We will show a design method for combinational circuits using the proposed basic circuits.