Title page for ETD etd-12082002-151511

Type of Document Master's Thesis
Author Syal, Manan
Author's Email Address msyal@vt.edu
URN etd-12082002-151511
Title Untestable Fault Identification Using Implications
Degree Master of Science
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Hsiao, Michael S. Committee Chair
Ha, Dong Sam Committee Member
Shukla, Sandeep K. Committee Member
  • Untestable faults
  • fault models
  • Implications
  • ATPG
  • symbolic simulation
Date of Defense 2002-12-06
Availability restricted
Untestable faults in circuits are defects/faults for which there exists no test pattern that can either excite the fault or propagate the fault effect to an observable point, which could be either a Primary output (PO) or a scan flip-flop. The current state-of-the-art automatic test pattern generators (ATPGs) spend a lot of time in trying to generate a test sequence for the detection of untestable faults, before aborting on them, or identifying them as untestable, given enough time. Thus, it would be beneficial to quickly identify faults that are redundant/untestable, so that tools such as ATPG engines or fault simulators do not waste time targeting these faults. Our work focuses on the identification of untestable faults at low cost in terms of both memory and execution time. A powerful and memory efficient implication engine, which is used to identify the effect(s) of asserting logic values in a circuit, is used as the basic building block of our tool. Using the knowledge provided by this implication engine, we identify untestable faults using a fault independent, conflict based analysis. We evaluated our tool against several benchmark circuits (ISCAS '85, ISCAS '89 and ISCAS '93), and found that we could identify considerably more untestable faults in sequential circuits compared to similar conflict based algorithms which have been proposed earlier.
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