Reference pulse verification circuit adaptable for engine control

Abstract

A reference pulse verification circuit is disclosed in which a sensor senses the passage of a number of teeth which project from a wheel rotated by an engine crankshaft. The projecting teeth are uniformly disposed about the wheel except for a missing tooth area corresponding to a predetermined angular reference position of the engine crankshaft. A missing pulse detector provides unverified reference pulses corresponding to the occurrence of the missing tooth reference position, and a verification counter is incremented in response to each sensor pulse produced in response to the passage of each rotating tooth. The counter output and the missing pulse detector output are combined such that a verified reference pulse is provided in response to each missing pulse detection which coincides with the occurrence of a predetermined tooth pulse count that was initiated after the occurrence of a preceeding missing pulse detection. In this manner spurious missing pulse detections can be differentiated from proper missing pulse detections which only occur after the passage of a predetermined number of teeth past the sensor. The count of the counter is reset in response to either the occurrence of a missing pulse detection and/or the attainment of a maximum count by the counter. The verified reference pulses are provided as an input to an engine control circuit which is enabled in response to the occurrence to the first verified reference pulse after the application of power to the control circuit.