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Effective TARO Pattern Generation

Effective TARO Pattern Generation. Intaik Park Ahmad Al-Yamani Edward J. McCluskey Sponsored by NFS and LSI logic. Stanford University Center for Reliable Computing. Outline. Introduction Preliminaries Algorithm Evaluation Experimental Result Conclusion.

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Effective TARO Pattern Generation

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  1. Effective TARO Pattern Generation Intaik Park Ahmad Al-Yamani Edward J. McCluskey Sponsored by NFS and LSI logic Stanford University Center for Reliable Computing

  2. Outline • Introduction • Preliminaries • Algorithm • Evaluation • Experimental Result • Conclusion

  3. Test escapes of ELF-Murphy chips • 100% SSF test • escapes • 100% transition test • escapes • TARO test (Transition fault propagated to All Reachable Output) • No escape

  4. Definitions • Reachable outputs : Outputs through which a fault can be propagated and be observed • Observable faults : Faults that an output can observe • Fault-output pair : A pair of fault site and one of its reachable output

  5. Example of fault-output pair a 1 b 2 c 3 4 d Fault site Output (PO+FF) fault-output pair

  6. Finding fault-output pairs 1. Observable faults for all outputs • by logical cone tracing • or by output mask setup 2. Reachable outputs for all fault sites • from observable faults 3. Fault site paired with a reachable output  fault-output pair

  7. TARO generation algorithm • Assign fault-output pairs • Only those that could be assigned at the same time • Use output masks • To control to which output a fault will be propagated

  8. TARO generation algorithm (contd.) • Generate tests for undetected • fault-output pairs • Exclude detected f-o pairs • Use output mask • - Control what output will observe the fault a 1 b 2 c 3 4 d Fault site Output (PO+FF) Detected f-o pair Undetected f-o pair

  9. TARO generation algorithm (contd.) • Assigned fault-output pairs: • fault a  output 1 • fault c  output 3 • fault d  output 3 • Output masks: • output 2, 4 • Fault b excluded a 1 b 2 c 3 4 d Fault site Output (PO+FF) Detected f-o pair Undetected f-o pair Assigned f-o pair

  10. TARO generation flowchart Start Find fault-output pairs ATPG with masks Fault simulation on each output All f-o pair detected? No Assign f-o pairs / masks Initial ATPG without masks Yes End

  11. TARO coverage • Traditional transition fault coverage • Not sufficient for TARO evaluation • Test metric required • To reflect number of reachable outputs used for each fault site # reachable outputs used Weight of fault = # total reachable outputs Σ weights of detected faults TARO coverage = # all faults

  12. ELF35 cores • 4 combinational cores (1 translator, 3 data paths) • 2 sequential cores (full-scanned 2901 processors)

  13. Test escapes of ELF35 * Number of escapes

  14. ELF35 Transition vs TARO test

  15. Conclusion • TARO tests generation method • + Using existing ATPG tool • + Very thorough test quality (no escapes) • - Long generation time • - Large pattern size • TARO  very thorough test • Sample-based quality assurance test • Metric to evaluate other tests • To which output a fault is sensitized matters

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