Determining Application-Specific Knowledge for Improving Robustness of Sequential Circuits

Due to their shrinking feature sizes as well as environmental influences, such as high-energy radiation, electrical noise, and particle strikes, integrated circuits are getting more vulnerable to transient faults. Accordingly, how to make those circuits more robust has become an essential step in today's design flows. Methods increasing the robustness of circuits against these faults already exist for a long period of time but either introduce huge additional logic, change the timing behavior of the circuit, or are applicable for dedicated circuits such as microprocessors only. In this paper, we propose an alternative method, which overcomes these drawbacks by determining application-specific knowledge of the circuit, namely the relations of flip-flops and when they assume the same value. By this, we exploit partial redundancies, which are inherent in most circuits anyway (even the optimized ones), to frequently compare the circuit signals for their correctness-eventually leading to an increased robustness. Since determining the correspondingly needed information is a computationally hard task, formal methods, such as bounded model checking, satisfiability-based automatic test pattern generation, and binary decision diagrams, are utilized for this purpose. The resulting methodology requires only a slight increase in additional hardware, does only influence the timing behavior of the circuit negligibly, and is automatically applicable to arbitrary circuits. Experimental evaluations confirm these benefits.