223_pdfsam_VLSI TEST PRINCIPLES & ARCHITECTURES

223_pdfsam_VLSI TEST PRINCIPLES & ARCHITECTURES -...

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192 VLSI Test Principles and Architectures z e d c b a ± FIGURE 4.26 Dynamic implications. e d c b a z f ± FIGURE 4.27 Another dynamic implications example. The intersection of ±a = 0 ²b = 0 ³ and ±b = 0 ³ is ±b = 0 ³ . In other words, the dynamic implication for z = 0 given c = 1is b = 0. Dynamic implications can also be applied to signals with a fault-effect. For instance, consider the circuit shown in Figure 4.27. Suppose there is a D on signal b , and this fault-effect is the only one for the current target fault. Then, in order to propagate the fault-effect to the primary output z , f = 1 is a necessary condition. This dynamic implication can be obtained via the following analysis. For b = D to propagate to z , either a = 0or c = 1 is needed, resulting in a fault effect at signal d or e . Regardless of which path the fault effect propagates, signal f = 1 is a necessary condition for the fault effect to propagate to z . Such an observation was made in [Akers 1976] [Fujiwara 1983].
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Unformatted text preview: The work in [Hamzaoglu 1999] extended this concept of dynamic implications a step further. Suppose the D-frontier for the current target fault consists of gates g 1 ²g 2 ²´ ´ ´ ²g n . By a similar analysis as the previous example shown in Figure 4.27, each gate g i ∈ D-frontier would have a set of necessary assignments, A i . Clearly, the necessary assignment for any single fault-effect may not be necessary for detecting the target fault. However, in order to propagate the fault effect to a primary output, at least one fault effect in the D-frontier must be sensitized to the output. Subse-quently, the intersection of all the necessary assignments for each of the gates in the D-frontier would be the set of required assignments for detection of the target fault....
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This note was uploaded on 05/16/2011 for the course ENGINEERIN mp108 taught by Professor Elbarki during the Spring '08 term at Alexandria University.

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