256_pdfsam_VLSI TEST PRINCIPLES & ARCHITECTURES

256_pdfsam_VLSI TEST PRINCIPLES & ARCHITECTURES -...

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Test Generation 225 Global State Space A B C Reached State Space D E Unexplored State Space ± FIGURE 4.45 State space exploration. Algorithm 14 LogicSimATPG 1: Identify reset signal masking for each primary input; 2: Partition the flip-flops (e.g., based on their controllability values.); 3: while stop condition not satisFed do 4: Generate test vectors that expand the search space the most using reset signal masking information and partition information; 5: Re-partition the flip-flops if desired; 6: end while fault coverage has been obtained for large sequential circuits with significantly less computational effort. For some circuits, the highest fault coverage was obtained compared with existing deterministic and simulation-based approaches. 4.8.3 Spectrum-Based ATPG Similar to logic-simulation-based ATPG, spectrum-based ATPG tries to seek embed-
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Unformatted text preview: ded properties in the fault-free circuit that can help with the test generation process. For spectrum-based ATPG, the underlying sequential circuit is viewed as a black-box system that is identifiable and predictable from its input/output signals, rather than the traditional view as a netlist of primitives. In studying a signal, the foremost concern is the predictability of the signal. If the signal is predictable, then a portion of it can be used to represent and reconstruct its entirety. Testing of sequential systems, then, becomes a problem of constructing a set of waveforms which when applied at the primary inputs of the circuit can achieve high fault coverages by exciting and propagating many faults in the circuit....
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