Multi-Terminal Routing with Length-Matching for Rapid Single Flux Quantum Circuits

With the increasing clock frequencies, the timing requirement of Rapid Single Flux Quantum (RSFQ) digital circuits is critical for achieving the correct functionality. To meet this requirement, it is necessary to incorporate length-matching constraint into routing problem. However, the solutions of existing routing algorithms are inherently limited by pre-allocated splitters (SPLs), which complicates the subsequent routing stage under length-matching constraint. Hence, in this paper, we reallocate SPLs to fully utilize routing resources to cope with length-matching effectively. We propose the first multi-terminal routing algorithm for RSFQ circuits that integrates SPL reallocation into the routing stage. The experimental results on a practical circuit show that our proposed algorithm achieves routing completion while reducing the required area by 17%. Comparing to [2], we can still improve by 7% with less runtime when SPLs are pre-allocated.