Evaluating Real Checkability for FPGA-based Components of Safety-Related Systems

Abstract

The paper focuses on the study of the checkability of digital circuits in relation to FPGA (Field Programmable Gate Array) components of safety-related systems that serve high-risk facilities, maintaining their functional safety in synergy with its own. Functional safety breaches are associated with failures that stimulate the use of fault-tolerant solutions. However, the possibilities of these solutions are limited by the number of failures which can be countered. As a result, functional safety, based only on circuit fault tolerance, faces the problem of multiple failures. This problem manifests itself in the example of hidden faults, which can be accumulated in significant quantities during extended normal operation of the system. The multiple manifestations of these faults in emergency mode call into question the fail-safety of fault-tolerant circuits, including FPGA components, which can accumulate faults in the memory of the LUT units. Ensuring the fail-safety of circuits requires taking into account their checkability, which depends on the data arriving at the inputs of the circuit in normal and emergency modes. A method for assessing checkability, which is important for the fail-safety of FPGA components, is proposed. Checkability is assessed on real input data, the change of which often extends only over a part of the range of values related to the normal functioning of the system. The method makes it possible to evaluate the change in the checkability of the circuit depending on the change in its input data.