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How the Diagnostician performs digital diagnostics.There are several scenarios in which the Diagnostician can be integrated into this overall environment - fault isolation for digital boards. These include: 1.) when no simulator is used, 2.) when a simulator is used, 3.) when a hot mock-up is being used for functional test When no simulator is being used When no simulation is being used, an engineer manually derives input test vectors and their output response. In this process, the engineer will normally build test vector blocks that test specific segments of circuitry at a time. In the end, he combines these test vector blocks into one test. If he was to use our tool, he would identify these blocks as separate tests, and identify the circuitry that they test to the Diagnostic Profiler. At run-time, the results of each test vector block is evaluated separately and provided to the Diagnostician. The Diagnostician uses the diagnostic knowledge base to interpret those results and provide, as appropriate, either the next best test (probe) or the faulty parts call-outs. When Simulation is being Used Given that modeling and simulation data exists, our approach is to modify the model input data to reflect that those points that will be probed exist at the edge. That way, when you run the "good circuit" simulation, you will get expected "good circuit" values for those probe points. These then are treated as tests that are available (columns). We will convert the resulting fault dictionary data into a Diagnostic Knowledge Base (DKB) format, and our Diagnostician, as is, will act as the fault dictionary look-up software does, plus provide probing advise. However, in this case, it is not a Guided Probe in the traditional sense, because it is not doing a pin-by-pin analysis, or trace-back, of the fault; it is using reasoning. It will actually find the fault quicker, with less extensive probing. So, we call it a "Reasoning Probe." |
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