SEQUENCE OF EVENTS DETECTION IN PROCESS CONTROL SYSTEM

摘要

PROBLEM TO BE SOLVED: To achieve the time stamp of an event without highly accurate or synchronized clocks in respective SOE(sequence of event detection) cards. SOLUTION: Free running counters located within each of sequence of events detection cards are used to mark each event with a counter value when the sequence of events detection card first detects the event. Indications of the event and of the counter value associated with a detected event are sent from each of the sequence of events detection cards to a corresponding controller which uses its secondary clock, a further free running counter and the value of a sequence of events counter assigned to the event to ascertain the actual or absolute time that the event was detected at the sequence of events card. The event and the absolute time for that event is then sent to a sequence of events reporting database, where this information is stored to form a system wide sequence of events log.