Application of asynchronous design to microcontroller startup logic

Abstract

Digital circuits designed today are almost exclusively clocked. As designs grow in size it becomes harder to effectively distribute the various clock signals over the circuit. The clock is also a big contribution to the power consumption of a circuit. Some work is being done to provide alternatives to standard synchronous design. One of these alternatives is the Balsa system.Several versions of an asynchronous module for controlling the startup process of a microcontroller was made in Balsa and compared to a standard synchronous implementation. Area estimates for the best asynchronous implementation gives a number that is a factor of over four larger than for the synchronous implementation. The asynchronous implementation has other advantages though. It has no dynamic power consumption when it is in a stable state. Additionally it can operate closer to the sub-threshold area.The asynchronous implementations have been tested and found working in active HDL. Balsa generated verilog netlists in a 350 nm library from the balsa language description. Design Compiler from Synopsys was used to get the area estimates. The asynchronous implementations shows potential, especially with regards to reduced power consumption.