A digital system and a method of operating a digital system wherein the digital system has a digital resource and an event detector detect events of the digital resource. An operational mode of at least one of the system and the digital resource in effect during an interval is determined and a number of events that occur during the interval is accumulated. The accumulated events are compared against at least one threshold associated with the operational mode and action is taken if the comparison indicates an out-of-nominal operation of the digital resource.