Functional Safety Analysis Techniques for Integrated Circuits Used in Cyber-Physical Systems

Abstract

Integrated Circuits (ICs) are used to realize multitude of real life systems. These real life systems have ICs interacting with physical systems (this combination being referred to as cyber-physical systems or hybrid systems) and many of them are used in safety critical applications. The implications of a fault in any of the constituent components of the system must be analysed and appropriately addressed to mitigate its potentially dangerous after effects. Given the increasing dependence on ICs to meet the functional requirements of safety critical applications, safety analysis of ICs plays an important role in ensuring safety of the application performed by the system. Today, safety analysis of ICs used in such systems is typically done in isolation of the end application and associated physical system due to practical considerations like safety analysis complexity, lack of a proper physical system model, etc. Many cyber-physical systems have an acceptable tolerance determined by the application due to the inertial nature of the physical system, error tolerance capability in closed loop applications, built-in hardware and software functionality, etc. These tolerances can be beneficially employed to reduce the hardware overhead required to implement safety. In this work, we investigate the problem of building affordably robust soft-error resilient systems based upon flip-flop protection. We develop methods to identify the minimal set of critical flip-flops which must be protected in an integrated circuit, keeping in mind the inherent tolerances (resiliency) of the system into which it is incorporated.