Abstract: A pick-up provides a square wave signal whose period corresponds to 720.degree. /N where N is the number of engine cylinders for a four stroke, two cycle internal combustion engine. An integrator is reset by both positive-going and negative-going edges of said square wave signal to produce a sawtooth waveform having a period equal to 360.degree. /N. A blanking circuit which is coupled with the pick-up blanks the sawtooth waveform of said integrator during alternate half cycles of the square wave. The blanked sawtooth waveform is supplied to one input of a comparator and a desired timing signal to the other input of said comparator. The comparator provides an engine timing signal when a predetermined relationship between the blanked sawtooth signal and the desired timing signal is attained. In this way, the engine timing signal is given once per cycle of said blanked sawtooth waveform with the timing thereof relative to said square wave being determined by the desired timing signal.

Abstract: A single pick-up coupled to sense engine crankshaft position can be utilized for both starting and running of the engine in an electronic spark timing advance control system. During starting, pulses from the pick-up are coupled via a zero crossing detector to the output ignition stage to cause spark plug firing at an essentially constant firing angle at or just slightly in advance of piston top dead center position. During running, the pulses from the pick-up reset, via a reset circuit, an integrator circuit so that a sawtooth waveform representative of engine crankshaft rotational position is developed. A desired timing signal derived from one or more parameters useful in controlling the time of ignition firing is compared against the sawtooth reference waveform and when a predetermined relationship between the two is attained, the ignition is fired. Should this predetermined relationship not be attained during a cycle of the sawtooth, the reset signal from the reset circuit forces ignition firing.