Design-for-Testability for Functional Broadside Tests under Primary Input Constraints

Functional broadside tests avoid overtesting of delay faults by creating functional operation conditions during the clock cycles where delay faults are detected. When a circuit is embedded in a larger design, a functional broadside test needs to take into consideration the functional constraints that the design creates for its primary input vectors. At the same time, application of primary input vectors as part of a scan-based test requires hardware support. An earlier work considered the case where a primary input vector is held constant during a test. The approach described in this article matches the hardware for applying primary input vectors to the functional constraints that the design creates. This increases the transition fault coverage that can be achieved by functional broadside tests. This article also considers the effect on the transition fault coverage achievable using close-to-functional broadside tests.