An effective silicon debug technique uses a trace buffer to monitor and capture a portion of the circuit response during its functional, post-silicon operation. Due to the limited space of the available trace buffer, selection of the critical trace signals plays an important role in both minimizing the number of signals traced and maximizing the observability/restorability of other untraced signals during post-silicon validation. In this thesis, a new method is proposed for trace buffer signal selection for the purpose of post-silicon debug. The selection is performed by favoring those signals with the most number of implications that are not implied by other signals. Then, based on the values of the traced signals during silicon debug, an algorithm which uses a SAT-based multi-node implication engine is introduced to restore the values of untraced signals across multiple time-frames. A new multiplexer-based trace signal interconnection scheme and a new heuristic for trace signal selection based on implication-based correlation are also described. By this approach, we can effectively trace twice as many signals with the same trace buffer width. A SAT-based greedy heuristic is also proposed to prune the selected trace signal list further to take into account those multi-node implications. A state restoration algorithm is developed for the multiplexer-based trace signal interconnection scheme. Experimental results show that the proposed approaches select the trace signals effectively, giving a high restoration percentage compared with other techniques. We finally propose a lossless compression technique to increase the capacity of the trace buffer. We propose real-time compression of the trace data using Frequency-Directed Run-Length (FDR) code. In addition, we also propose source transformation functions, namely difference vector computation, efficient ordering of trace flip-flops and alternate vector reversal that reduces the entropy of the trace data, making them more amenable for compression. The order of the trace flip-flops is computed off-chip using a probabilistic algorithm. The difference vector computation and alternate vector reversal are implemented on-chip and incurs negligible hardware overhead. Experimental results for sequential benchmark circuits shows that this method gives a better compression percentage compared to dictionary-based techniques and yields up to 3X improvement in the diagnostic capability. We also observe that the area overhead of the proposed approach is less compared to dictionary-based compression techniques. / Master of Science

Les technologies nanométriques ont réduit la fiabilité des circuits électroniques, notamment en les rendant plus sensible aux phénomènes extérieurs. Cela peut provoquer une modification des composants de stockage, ou la perturbation de fonctions logiques. Ce problème est plus préoccupant pour les mémoires, plus sensibles aux perturbations extérieures. Les codes correcteurs d'erreurs constituent l'une des solutions les plus utilisées, mais les contraintes de fiabilité conduisent à utiliser des codes plus complexes, et qui ont une influence négative sur la bande passante du système. Nous proposons une méthode qui supprime la perte de temps due à ces codes lors de l'écriture des données en mémoire, et la limite aux seuls cas où une erreur est détectée lors de la lecture. Pour cela on procède à la décontamination du circuit après qu'une donnée erronée ait été propagée dans le circuit, ce qui nécessite de restaurer certains des états précédents de quelques composants de stockage par l'ajout de FIFO. Un algorithme identifiant leurs lieux d'implémentation a également été créé. Nous avons ensuite évalué l'impact de cette méthode dans le contexte plus large suivant : la restauration d'un état précédent de l'ensemble du circuit en vue de corriger une erreur transistoire susceptible de se produire n'importe où dans le circuit. / Nanometric technologies led to a decrease of electronic circuit reliability, especially against external phenomena. Those may change the state of storage components, or interfere with logical components. In fact, this issue is more critical for memories, as they are more sensitive to external radiations. The error correcting codes are one of the most used solutions. However, reliability constraints require codes that are more and more complex. These codes have a negative effect on the system bandwidth. We propose a generic methodology that removes the timing penalty of error correcting codes during memory's write operation. Moreover, it limits the speed penalty for read operation only in the rare case an error is detected. To proceed, the circuit is decontaminated after uncorrected data were propagated inside the circuit. This technique may require restoring some past states of few storage components by adding some FIFO. An algorithm that identifies these components was also created. Then we try to evaluate the impact of such a technique for the following issue: the global state restoration of a circuit to erase all kinds of soft errors, everywhere inside the circuit.