Abstract: A frequency determination system and method for frequency determination. A programmable controller responds to receipt of a sequence of pulses. A number of interrupts of different priority level perform rate or frequency calculation in an efficient manner. Pulses are counted upon receipt but the actual rate calculation is performed by a low priority software routine. By performing only essential counting functions when pulses occur, the programmable controller can perform other tasks in addition to the rate calculations. In the disclosed design, the controller can monitor serial communications in addition to performing the rate calculation task.