Improving the accuracy of circuit activity measurement

Abstract

A novel measure of activity in digital circuits, called transition density, along with an efficientalgorithm to compute the density at every circuit node, has been proposed in [1]. However, the efficiency of this algorithm is achieved at the cost of accuracy in the density values. This leaves much to be desired for its use in applications which require more accurate activity measurements at each node in the circuit e.g., circuit optimization problems with a low power goal. The complexity of this problem lies in computing the Boolean difference probabilities at each node of the circuit. In this paper, an efficientalgorithm for computing these probabilities is described. This allows the activity measurements, within a circuit partition, to be carried out in a more efficientmanner compared to the well known approach of computing these probabilities. Larger circuit partitions, where each node within a partition is solved accurately with respect to that partition, result in more accurate activity measurements. An efficientcircuit partitioning algorithm, with the goal of maximizing the number of correlated nodes within each partition, has been developed. This allows more accurate measurements compared to a randomly selected set of partitions. These methods have been incorporated in an improved simulator for circuit activity measurement. Some results obtained on the ISCAS85 benchmark circuits are included.