A new design approach for RSFQ logic circuits based on the binary decision diagram

We will propose a new design approach for single-flux-quantum (SFQ) logic circuits based on a binary decision diagram (BDD). The BDD is a way to represent a logical function by using a directed graph, which is composed of nodes having one input (root) and two outputs (branches). The node has binary states internally which can be controlled from outside, and it switches a messenger entering from the root into one of two branches depending on the internal state. It has been proven that any combinational logic can be represented by this basic element. We will show that the BDD is effectively implemented by an SFQ circuit, where the node is replaced with an SFQ D/sub 2/ flip-flop. Important features of the BDD SFQ logic circuit are simplicity of circuit structure, self-timed nature and high modularity. We have designed a BDD SFQ adder and showed that the junction count and latency are smaller than that of the conventional RSFQ adder.