Built in Test - coverage and diagnostics

Idealy, everyone would like to embed test into their products today, whether it´s to reduce costs, build in support capabilities, ensure better quality, reduce dependacy on expert technicians, or for one of many other intelligent motivations. However, it seems the technology of Built in Test (BIT) has not taken off or been adopted like many believed it would. The reasons for this poor adoption are diverse: some blame it on design, others fault product specifications and even others blame it on the fundementals of the technology itself. The underlying root cause of slow BIT adoption may be a result of an inaccurate belief that designing an embedded test is more difficult than designing any other test. In reality, understanding what to embed is simply a function of knowing the coverage you are seeking and at what level you want to be able to diagnose the problem when a failure occurs. Presented in this paper are several considerations on how to best approach Built in Test. This preferred approach is illustrated by explaining the importance of understanding how to achieve effective and appropriate coverage levels, while also maintaining a useful level of diagnostic resolution. Understanding and application of these concepts will effectively enable optimal design and implementation of Built in Test.