Metric for the ability of functional capture cycles to ensure functional operation conditions

Abstract

Several test generation procedures are based on the expectation that after clocking a circuit in functional mode for several clock cycles, the circuit enters its functional state space and operates under functional operation conditions. Functional operation conditions are important for avoiding overtesting of delay faults. This study develops a quantitative metric for assessing the ability of functional capture cycles to take the circuit into its functional state space, and ensure functional operation conditions. The metric is based on the distances between the states that the circuit traverses during functional capture cycles and reachable states that the circuit can enter during functional operation. The paper also describes a procedure for modifying a test set so as to reduce the values of the metric for its tests.