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Fault Diagnosis

Fault Diagnosis. The Diagnosis Problem. General: Given the symptoms, determine the likely cause(s) Applies to many domains: Human illness, trouble-shooting of any kind

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Fault Diagnosis

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  1. Fault Diagnosis

  2. The Diagnosis Problem • General: Given the symptoms, determine the likely cause(s) • Applies to many domains: Human illness, trouble-shooting of any kind • In testing: Given test results on a failing device, {<failing test, failing outputs>}, find the likely defects/faults as the causes. • Often a preprocess to failure-mode analysis (FMA), an expensive process. SAT-Based Diagnosis

  3. Model-based vs. Model-free Diagnosis? • Model Based: Assumes the error-causing defect can be modeled by one or more of the standard fault models: SAF, Bridging, Opens, ... • Model-Free: Assumes the defect can excite any number of lines in any time frame, some of whom are observed in the same or later time frames according to the test results. Both, however, must limit the multiplicity of causes for practical reasons. SAT-Based Diagnosis

  4. Cause-effect vs. Effect-cause Analysis? • Cause-effect: • For the given test, pre-compute the effects of all possible causes, according to an assumed fault model, and build a dictionary with effects as index and causes as contents • Diagnosis reduces to simple dictionary lookup • Effect-cause • Analyze the circuit elements connected to the outputs for observed test results and determine likely causes at the inputs of the circuit elements. • Repeat the process recursively until all possible causes are determined. SAT-Based Diagnosis

  5. Motivating Example • Consider test results from c17: We will work through the example in class. SAT-Based Diagnosis

  6. Motivating Example (Contd.) • Now consider the results of a third test vector applied to c17: SAT-Based Diagnosis

  7. Fault Diagnosis Using Boolean Satisfiability* * A. Smith, A. Veneris, M. F. Ali, and A. Viglas, “Fault Diagnosis and Logic Debugging Using Boolean Satisfiability,” IEEE TCAD, 24(10), Oct 2005, 1606-1621.

  8. Modeling Candidate Fault Location SAT-Based Diagnosis

  9. Counter for Multiple Faults SAT-Based Diagnosis

  10. Complete Construction SAT-Based Diagnosis

  11. Example Sequential Circuit and its ILA Representation SAT-Based Diagnosis

  12. Diagnosis in Two Cycles SAT-Based Diagnosis

  13. Sequential SAT Based Diagnosis-1 SAT-Based Diagnosis

  14. Sequential SAT Based Diagnosis-2 SAT-Based Diagnosis

  15. Two-Pass Diagnosis Using Structure Information SAT-Based Diagnosis

  16. Model-Based Diagnosis - SAFs SAT-Based Diagnosis

  17. Experimental Results - 1 SAT-Based Diagnosis

  18. Experimental Results - 2 SAT-Based Diagnosis

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