RustSFQ: A Domain-Specific Language for SFQ Circuit Design

Cell-based design of a single-flux-quantum (SFQ) digital circuit requires input-output consistency; every output signal must be consumed only once by the input of the following component, which is a unique constraint, unlike the traditional CMOS digital circuit design. While there are some cell libraries and simulation tools for SFQ circuit development, they do not verify the input-output consistency, and designers have significant responsibilities to ensure it manually. Additionally, designers have to carefully manage net names without unintended duplication and correct connectivity among nets in a netlist for simulations. We propose RustSFQ, a domain-specific language (DSL) embedded in Rust that automatically ensures the input-output consistency in the SFQ circuit by leveraging the ownership system of Rust. Each SFQ circuit element is represented as a function while wires are represented as instances, and the Rust compiler verifies that multiple elements do not share a single wire through the ownership system. Circuit descriptions in the RustSFQ are successfully compiled into low-level netlists for both analog and digital circuit simulations, and the DSL provides higher productivity than the conventional design flow. Using the RustSFQ, we developed an SFQ-based Reed-Solomon encoder with a 4-bit width for the first time as a case study. We confirmed that the circuit operated correctly at 10 GHz through circuit simulations.