Fault detection in a tristate system environment

We present a novel approach for detecting faults in tristate system environments-e.g., in multiple board systems. These environments are made of an interconnect and drivers/receivers with tristate features. We present a comprehensive fault model that includes faults in terminals (drivers/receivers) and nets. Under this fault model, physical faults (stuck-at and short), as well as functional faults (dominance, permanently enabled or permanently disabled driver modes), are taken into account. We show that, far a single net with L drivers, 2L tests are necessary and sufficient for fault detection. This is independent of the number of receivers. We extend this result to a system environment with N nets and where K is the maximal number of drivers for a net. Under the proposed fault model, any number of faults of any types can be detected in a system environment using max(2K, P) tests, where P is the minimal integer that satisfies C-P/2(P) greater than or equal to N. If only the traditional (wired-AND or wired-OR) model is assumed, then the lest set required for fault detection can be further reduced. We provide simulation results and show that the proposed approach outperforms previous methods found in the technical literature.