Functional testing of rapid single-flux-quantum (RSFQ) logic circuits
at high speed is necessary to further optimize circuit design, but it
is not easy to do off-chip testing because of the high speed and small
amplitude of SFQ pulses, This paper will present the design and test
results of an 20 Gb/s bit-by-bit on-chip high-speed digital test syste
m based on data-driven self-timed (DDST) circuits.