A PES for use in highly safety-critical control

The programmable electronic systems currently employed in safety-critical control implement either strictly periodical or task-based operation. Here, a concept combining the advantages of both principles is presented. Its most essential characteristics are task execution without the use of asynchronous interrupts, and a tightly integrated hardware scheme to detect processing failures, for non-intrusive monitoring, and forward recovery at runtime. The architecture builds up on physical separation of task execution and task administration, which is implemented in form of a digital circuitry. Time is quantised into execution intervals, and tasks are partitioned into execution blocks matching these intervals. This concept lowers the complexity of both hardware and temporal behaviour and, thus, conforms particularly well with the requirements of the safety standard IEC 61508