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Fault Model Single Stuck at Fault Design Representation

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					     Fault Model: Single Stuck at
                Fault
     Design Representation level:
             Gate Level
     Single Stuck at 0 or 1 Fault

X1
            G1
                                    G5
X2
                           G3
X3
            G2
X4                                  G6
                           G4
X5
     How to Detect a Fault

     Stuck at 1 Fault

X1
         G1
                             G5
X2
                        G3
X3
         G2
X4                           G6
                        G4
X5
     Step #1: ‘Controlability’
     Stuck at 1 Fault

X1
         G1
                                        G5
X2
                        G3
X3
         G2
X4                                      G6
                        G4
X5

                   Sensitize fault - control input path to fault
         Step #1: ‘Controlability’
         Stuck at 1 Fault
                       Fault ckt: 1
X1   1
                       correct ckt: 0
             G1
                                            G5
X2
     1                     G3
X3
             G2
X4                                          G6
                           G4
X5

                       Sensitize fault - control input path to fault
         Step #2: ‘Observability’
         Stuck at 1 Fault
     1
X1
             G1
                                           G5
X2
                            G3
X3 1
             G2
X4                                         G6
                            G4
X5


                    Propagate ‘fault’ to output pin
           Step #2: ‘Observability’
           Stuck at 1 Fault

X1 1                                                    Observe fault
               G1
                                             G5          0 : faulty ckt
X2     0                             1                   1 : correct ckt
                              G3
X3 1                  -
               G2
X4 -                                  -      G6
                              G4                        -
X5 -


                      Propagate ‘fault’ to output pin
      Detect a different fault
     Stuck at 0 Fault

X1
         G1
                             G5
X2
                        G3
X3
         G2
X4                           G6
                        G4
X5
           Simplify this process by
          detecting stuck at D fault
          Stuck at D Fault
     D
X1                                ¯
                                  D
              G1                                        D
                                             G5
      0
X2                                    1
      1                      G3
X3                    -
      -       G2                                    -
X4                                    -      G6
    -                        G4
X5
   Test Pattern                                   Test Response

 Test Vector is (input stimulus , output response)=(D 0 1 - - D -)=
 ((0 0 1 - - 0 -) (1 0 1 - - 1 -))=((0 0 1 0 0 0 0)(1 0 1 0 0 1 0))
     X1 X2 X3 X4 X5 Z1 Z2 Stuck at Faults detected on wires
     D 0 1 - - D -           x1,a
     - D 0 0 - D -           x2,b
     - 1 D 1 0 - db         x3,c,d,z2
     - 0 0 - D - D           x5,d,z2
     - 0 1 D 1 - db         x4,c,d,z2

X1                         a
               G1                                    Z1
                                           G5
X2                                   b
                               G3
X3                    c
               G2                                   Z2
X4                                  d      G6
                               G4
X5
                          Undetectable fault ...
        SSA-D fault

D               D

1                              D

0?                    D                   ?

1?
       1



Need to set this wire to 1 for observability
and 0 for controlability
FF                FF        FF


         CL            CL


FF                FF        FF


     Scan Chain
 Random Patterns and Fault
       Coverage
100%

                      Fault Coverage




       Number of Pseudorandom patterns

				
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posted:4/3/2010
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