Detecting a relative shaft position on geared shafts

A digital logic circuit, comprising:

• a primary gear revolution counter configured to detect an input signal corresponding to teeth of a phonic wheel having a same rotation rate as a primary gear and to output a primary gear revolution signal upon detecting N teeth of the phonic wheel, where N is a number of teeth of the phonic wheel greater than one and less-than-or-equal-to a total number of teeth of the phonic wheel;
• a primary gear tooth pulse generator configured to receive the primary gear revolution signal and to generate a primary gear tooth pulse at a first interval of time corresponding to an interval of time at which a tooth of the primary gear passes a predetermined location;
• and
• a secondary gear revolution pulse generator configured to generate a secondary gear revolution signal upon detecting Z primary gear tooth pulses, wherein Z corresponds to a total number of teeth of a secondary gear.

A method comprising:

• receiving position signals corresponding to teeth of a phonic wheel, the phonic wheel fixed with respect to a primary gear, the primary gear rotatably engaged to a secondary gear;
• generating a primary gear revolution signal corresponding to a full revolution of the primary gear based on the detected position signals;
• generating primary/secondary gear tooth pulses corresponding to time intervals at which teeth of the primary and secondary gears pass a predetermined location based on the primary gear revolution signal;
• and
• generating a secondary gear revolution signal corresponding to a time interval at which the secondary gear completes a full revolution based on the primary/secondary gear tooth pulses.