Implementing asynchronous logic in COTS FPGAs

What does asynchronous mean?
In an asynchronous circuit, parts are largely autonomous. They are not governed by any regular, periodic time-controlling mechanism, such as a clock circuit or signal, but instead need only wait for the signals that indicate completion of instructions and operations. These signals are often specified by simple data transfer protocols.
This digital logic design is contrasted with a synchronous circuit which operates according to clock timing signals.