Abstract: A method and system is provided for a nuclear reactor safety related application. The method includes executing two forms of a same application-specific logic, one of the two forms implemented as hardware logic, and the other of the two forms implemented as software instructions for execution by microprocessor-based controlling software. Each form of the application-specific logic is executed with a same set of inputs. The method compares a result produced from the execution of the hardware-implemented form to a result produced from the execution of the software-implemented form. When the compared results concur, the controlling software performs actions associated with the concurring results by executing microprocessor-based software. When the compared results fail to concur, the controlling software reports the failure of the compared results to concur to an operator by executing microprocessor-based software, and thereafter places the microprocessor-based software system into an inoperative (INOP) mode.

Abstract: A method for operating a controller having a number of timers to thereby control a plurality of events greater than the number of timers, includes, between clock ticks, receiving one or more signals from sensors, switches, executing programs, or a combination therefore that initiate one or more timed events. After a clock tick immediately following the receiving of the one or more signals, the method further includes updating entries in an event control block in accordance with the received signal or signals. The entries include a time remaining for pending events, a time past due for active events, and a priority of each event. The method further includes determining whether any pending event or events have timed out, activating any timed out events, and sending a signal notifying an executing program of the activated event having the highest priority.