An RSFQ Superconductive Programmable Gate Array

Field-programmable gate arrays (FPGAs) allow circuit reconfiguration in the field, which adds to the flexibility of electronic systems. Applied to superconductive electronics, reprogrammability allows system functionality to be changed without remanufacturing the circuit or dismantling a cryogenic setup. We discuss the design issues relevant to a superconducting programmable gate array (SPGA), and report an elementary 4200-junction SPGA. The SPGA is built around interconnected 2-input logic blocks which contain 4-bit lookup tables. Designs for the programming frame, address decoding, lookup tables and switch implementations are discussed, together with design constraints imposed by the unidirectional nature and large size of single flux quantum (SFQ) transmission lines.