Despite the growing interest in asynchronous circuits, programmable
asynchronous controllers based on the idea of microprogramming have not
been actively pursued. Since programmable control is widely used in many
commercial ASICs to allow late correction of design errors, to easily
upgrade product families, to meet the time to market, and even effect
run-time modifications to control in adaptive systems, we consider it
crucial that self-timed techniques support efficient programmable
control. This is especially true given that asynchronous (self-timed)
circuits are well suited for realizing reactive and control-intensive
designs.  We offer a practical solution to programmable asynchronous
control in the form of application-specific microprogrammed asynchronous
controllers (or microengines). The features of our solution include a
modular and easily extensible datapath structure, support for two
main styles of handshaking (namely two-phase and four-phase), and many
efficiency measures based on exploiting concurrency between operations
and employing efficient circuit structures. Our results demonstrate that
the proposed microengine can yield high performance - in fact
performance close to that offered by automated high-level synthesis
tools targeting custom hard-wired burstmode machines.