Towards a Complete Methodology for Synthesizing Bundled-Data Asynchronous Circuits on FPGAs

Asynchronous circuits are gaining momentum as a promising low-power alternative to the conventional synchronous design approaches. In particular, single-rail bundled-data design style has seen significant interest both for designing GALS systems and in the emerging area of neuromorphic computing. However, there has been only limited research on implementing these asynchronous circuits on commercial FPGAs, which can be challenging due to the use of relative timing constraints in these designs for correct operation. This paper proposes a systematic CAD methodology to synthesize efficiently bundled-data asynchronous circuits on commercial FPGAs, achieving a two-fold goal for the target implementation: robustness and high performance. The methodology is targeted to the existing Xilinx Vivado tool set. As a case study, two asynchronous NoC switches are prototyped on Xilinx Virtex 7 in 28 nm: one supporting unicast, and the other also handling multicast. The former shows significant energy and idle power improvements, with some performance benefits, over a high-performance synchronous FPGA-based switch. The asynchronous multicast router also shows promising energy and performance results. Although a NoC case study is used, the proposed approach is general and can be used for other bundled-data asynchronous circuits.