  Rapid Single Flux Quantum (RSFQ) logic is a promising technology to supersede
Complementary metal-oxide-semiconductor (CMOS) logic in some specialized areas
due to providing ultra-fast and energy-efficient circuits. To realize a
large-scale integration design, electronic design automation (EDA) tools
specialized for RSFQ logic are required due to the divergences in logic type,
timing constraints, and circuit structure compared with CMOS logic. Logic
synthesis is crucial in converting behavioral circuit description into circuit
netlist, typically combining combinational and sequential circuit synthesis.
For the RSFQ logic, the sequential circuit synthesis is challenging, especially
for non-linear sequential blocks with feedback loops. Thus, this paper presents
a sequential circuit synthesis algorithm based on finite state machine (FSM)
decomposition, which ensures design functionality, lowers costs, and improves
the RSFQ circuit performance. Additionally, we present the synthesis processes
of the feedback logic and the 2-bit counter to demonstrate how the proposed
algorithm operates, and ISCAS89 benchmark circuits reveal our method's ability
to synthesize large-scale sequential circuits.
