Application - Speci c Programmable Control for High Performance Asynchronous Circuits

| The advantages of the programmable control paradigm are widely known in the design of synchronous sequential circuits: easy correction of late design errors, easy upgrade of product families to meet time to market constraints, and modi cations of the control algorithm, even at run-time. However, despite the growing interest in asynchronous (self-timed) circuits, programmable asynchronous controllers based on the idea of microprogramming have not been actively pursued. In this paper, we propose an asynchronous microprogrammed control organization (called a microengine) that targets application-speci c implementations, and emphasizes simplicity, modularity, and high performance. The architecture takes advantage of the natural ability of self-timed circuits to chain actions e ciently without the clock-based scheduling constraints that would be involved in comparable synchronous designs. The result is a general approach to the design of application-speci c microengines featuring a programmable datapath topology that o ers very compact microcode and high performance|in fact performance close to that o ered by automated highlevel synthesis tools targeting state-of-the-art asynchronous hard-wired controllers. In performance comparisons of a CD-player error decoder design, the proposed microengine architecture was 26 times faster than the general purpose hardware of a 280 MIPS microprocessor, over 3 times as fast as the special purpose hardware of a low-power macromodule based implementation, and was even slightly faster than a nite state machine based implementation. Keywords| programmable control, microprogram, microcontrol, microengine, chaining, asynchronous circuits, selftimed, application-speci c, architecture, ASIC