Quantitative analysis methodology in safety-critical microprocessor applications

In this paper, a quantitative methodology to be considered in safety-critical microprocessor applications is proposed. Some important aspects that must be considered in safety analysis work are discussed. We discuss how to evaluate the dangerous detectable and undetectable system failure rates in a single microprocessor board and the mean time to unsafe failure (MTTUF) of a critical system. The proposed methodology is finally applied to a practical system which employs a triple modular redundancy (TMR) architecture. The results obtained by employing this methodology are extremely relevant, especially to those aspects related to the impact of the computational blocks in the final safety integrity level (SIL) of a critical system. In this paper, we also consider how the software can influence the evaluation of the fault cover factor, another important aspect in safety analysis work.