Introducing deglitched-feedback plus convergent encoding for straight hardware implementation of asynchronous finite state machines

Asynchronous finite state machines (AFSMs) are of interest in a number of areas, particularly when simplifying the hardware and/or reducing power consumption are essential. The design of reliable standalone (no handshake signals needed) AFSMs, however, is complex due to especially possible signal races, which seriously limit their widespread use. We introduce a fundamental modification, which consists of replacing the delays in the feedback loop with deglitchers. This simple modification, combined with a proposed convergent state encoding, allows standalone AFSMs to finally be implemented nearly as easily as conventional (synchronous) FSMs, even for burst-mode operation. A helpful tool for analyzing AFSMs is also introduced. The benefits of the proposed approach are confirmed in the experiments, developed with VHDL and FPGAs.