Automatic selection of efficient observability points in combinational gate level circuits using particle swarm optimization

Abstract

The ever-increasing size of digital circuits makes the process of testing such designs more complex everyday. This complexity leads to more complicated logic cones, which results in harder to control and observe nodes in digital circuits. Reduced controllability and observability will decrease circuit's fault coverage, resulting in harder to test circuits.Addition of test points, which enables us to control and observe nodes, can give the test engineer direct access to these locations. From another perspective, addition of observability points is more economical in terms of silicon area than adding control points. Still, observability points must be carefully chosen to reduce hardware overhead and gain better fault coverage.In this paper, we select the minimal set of observability points to obtain the maximum coverage. For this purpose, a novel method based on particle swamp optimization (PSO), which is a bio-inspired optimization algorithm, is adopted so that it automatically selects the efficient observability points in order to increase the fault coverage. One should note that this is an offline method which is performed only once for each circuit.