A real-time PES supporting runtime state restoration after transient hardware-faults

Controlling safety-critical real-time applications that cannot immediately be transferred to a safe state requires highly reliable programmable electronic systems (PESs). This demand for fault-tolerance is usually satisfied by applying redundant processing structures inside each PES and, additionally, configuring multiple PES redundantly. Instead of minimising the failure probability of single PESs, it is also desirable to provide a redundant configuration of PESs with the capability to re-start single units at runtime. This requires copying a PESs internal state at runtime, since a re-started unit must equalise its internal state with that of its redundant counterparts before the redundant processing can be rejoined. As a result, redundancy attrition due to transient faults is prevented, since failed channels can be brought back on line. This article states the problems concerned with runtime state restoration of real-time systems, discusses the advantages and disadvantages of existing techniques and introduces a hardware-supported state restoration concept