Improved Diagnostic Capabilities of Avionic Systems Containing Boundary Scan Technology

The objective of this project is to exploit the boundary scan technology that resides within modern military electronics in order to improve the item's diagnostic capability. Boundary scan technology was designed to improve the testability and diagnosability of electronics. Its use, however, has been primarily focused on finding manufacturing faults, such as shorts, opens, missing and dead components. Tools are also geared for manufacturing tests. Predominant failure modes in US Navy fielded units are usually caused by non-catastrophic and out of tolerance conditions and these are different than production defects. Boundary scan, however achieves testability by facilitating different configurations than the normal operational one. Special test configurations can improve diagnosability as well, though to date only the testability aspects have been utilized. We show how diagnosability is improved with existing standardized IEEE-1149.1 features, like SAMPLE and EXTEST. We also propose novel uses of boundary scan to augment BIT and further reduce diagnostic complications. These new instructions will further improve diagnosability without requiring circuit design or even test programming changes. They will, instead, involve the manipulation of boundary scan data to configure the system under test to increasingly more diagnosable configurations. We propose developing user friendly software that implements diagnostician commands and performs the cumbersome boundary scan data manipulations needed to achieve reconfigurations. Improvements will allow fault isolation to a single WRA in nearly 100% of the cases. They will also help other diagnostic complications, such as cannot duplicates, retest OK, no fault found, erroneous fault isolation and false alarms.