Pulsar: Constraining QDI Circuits Cycle Time Using Traditional EDA Tools

Asynchronous quasi-delay-insensitive (QDI) circuits are known for their potentially enhanced robustness to PVT variations when compared to synchronous circuits or to bundled data asynchronous design. They are also a good choice for high performance circuits used to solve several real-world problems. However, it is often difficult to constrain the minimum performance for QDI circuits. Thus, enhancing the synthesis quality for QDI design is a justifiable effort, especially in rising application fields, such as the Internet of Things and Artificial Intelligence. This work proposes Pulsar, a method based on the extension of SDDS-NCL, a previously proposed asynchronous QDI template and design flow. Pulsar brings four original contributions: (i) two new models for components used to as sequential barriers; (ii) a new model for half buffer pipelines, half-buffer channel network (HBCN); (iii) a linear programming formulation to define a circuit cycle time constraint; (iv) a design flow that enables automating the process to design sequential SDDS-NCL circuits. Experiments comparing synthesis results with Pulsar of a 6-stage, multiply-accumulate (MAC) show that it can guarantee a maximum cycle time of 3.2ns, while the original Unclesynthesised circuit without logic optimisation leads to timing violations at a 6ns constraint.