Boundary scan as a system-level diagnostic tool

Boundary scan is a testability tool intended to provide independent observability and controllability at the periphery of the IC. For the past two decades, it has been used successfully in manufacturing tests to identify shorts, opens and other manufacturing defects. Until now, however, it has not been widely used as a system level diagnostic tool, especially to diagnose military systems requiring field replacement or repair. In this paper, we show that the benefits of boundary scan are as compelling for the support environment as they are to manufacturing test. An important advantage is that with this technology, tests and diagnoses can be created without requiring intimate knowledge of the circuit design. This is significant as military systems use more commercial off the shelf (COTS) equipment, where schematics are either unavailable or unreliable. The metrics for fault isolation are different from those for fault detection, but as we shall demonstrate, systems containing boundary scan are considerably more diagnosable than those without.