US Patent 7676530 Duration minimum and maximum circuit for performance counter

A circuit for tracking the minimum and maximum duration of an event of interest is described. The circuit is connected to a counter for counting a number of clock cycles that the event of interest is active and comprises logic for detecting deactivation of the event of interest and generating a duration end signal; logic responsive to the duration end signal for comparing a count value with a shadow value; and logic for updating the shadow value based on results of the comparing.