falut collapsing
TRANSCRIPT
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TOPIC : Fault collapsing due to faultequivalence and fault dominance
UNIT 2 : Fault modeling
Module 2.3 Fault edundanc! and Faultcollapsing
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Fault collapsing
T"e num#e of faults t"at need to#e simulated can #e deceased#! e$ploiting t%o elations
#et%een a pai of faults fiand f&:a' Fault equivalence
#' Fault dominance
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Collapsed (atio
Man! of t"e faults ae emoveddue to fault equivalence and faultdominance.
Collapsed atio is t"e atio ofemaining faults and totalnum#e of faults.
Collapsed atio :)Total Faults * Fault emoved' +
Total fault.
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Fault equivalence
Defnition :
Two faults of a Boolean circuit arecalled equivalent i they transform
the circuit such that the two faultycircuits have identical outputfunctions. Equivalent faults arealso called indistinguishable and
have exactly the same set of tests.,$ample: -n input line sa/ and output
line sa/ in an -N0 gate.
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Fault equivalence
T%o faults 1 and f& in a cicuit ae said to #eequivalent if t"e coesponding fault! vesionsof t"e cicuit ae identical. In ot"e %ods alltests t"at detect 1 also detect f&.
Num#e of fault sites in a gatelevel cicuit PI)pima! inputs' 4gates 4 )fanout#anc"es'
-n ninput 5oolean gate equies onl! )n6'instead of )2n2' single stuc7at faults to #emodeled #ecause of equivalent fault collapsing.
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Fault equivalence :e$ample
8tuc7at/ at output of -N0 gate isequivalent to stuc7at/ at t"e input
pins.
8o9 %"ile testing %e can emovet"e 2 stuc7at/ fault at t"e input
pins9 since t"ese t%o fault %ill #e
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,quivalent fault collapsing fo5oolean gates
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Fault equivalence : cicuit
Fault deleted due to equivalent faultcollapsing
Collapsed atio : 6+3/ /.;33
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Fault dominance
Denition !f all tests of fault"# detect another fault "$%then "$ is said to dominate
"#. The two faults are alsocalled &conditionally'equivalent with respect to
the test set of "#. (hen twofaults "# and "$ dominateeach other% then they areequivalent.
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Fault dominance
f and g aefunctionall! equivalent unde T.
In ot"e %ods9 i> dominates g9 t"enan! test t t"at detects g.
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Fault dominance :,$ampleA 3-input AND gate.1 ? sa6 fault in one input of t"e
gate
f& ? sa6 in t"e gate output Tests fo 1 ? /66
Tests fo f& ? ///9 //69 /6/9 /669 6//96/69 66/
T"us9 f& dominates 1 .
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Fault dominance : cicuite$ample
Collapsed atio : 62+3/ /.@/