ATPG-based grading of strong fault-secureness

Robust circuit design has become a major concern for nanoscale technologies. As a consequence, for design validation, not only the functionality of a circuit has to be considered, but also its robustness properties have to be analyzed. In this work we propose a method to verify the strong fault-secureness by use of constrained SAT-based ATPG. Strongly fault-secure circuits can be seen as the widest class of circuits achieving the totally self-checking (TSC) goal, which requires that every fault be detected the first time it manifests itself as an error at the outputs. As the strongly fault-secure property guarantees to achieve the TSC goal even in the case of fault accumulation, the effects of all possible fault sequences have to be taken into consideration to verify this property. To speed up the complex analysis of multiple faults we develop rules to derive detectability or redundancy information for multiple faults from the respective information for single faults. For the case of not strongly fault-secure circuits our method provides measures to grade the ldquoextentrdquo of strong fault-secureness given by the implementation.