Testing of Asynchronous Designs by "Inappropriate" Means: Synchronous Approach

The roadblock to wide acceptance of asynchronous methodology is poor CAD support. Current asynchronous design tools require a significant re-education of designers, and their capabilities are far behind synchronous commercial tools. This paper considers the testing methodology for a particular subclass of asynchronous circuits (Null Convention Logic or NCL) that entirely relies on conventional CAD tools available at today’s market. It is shown that for acyclic NCL pipelines a test pattern generation for stuckat faults could be effectively solved through the construction and checking of the synchronous circuit with a set of faults “equivalent” to the original NCL circuit. This result is extended to arbitrary NCL structures by applying the partial scan technique to break computational loops. The method guarantees 100% stuck-at fault coverage in NCL systems, which is confirmed by experimental data.