1. An electronic ignition timing control system for electronically controlling the ignition timing of an internal combustion engine having a crankshaft and having associated therewith ignition means responsive to an ignition signal applied thereto for effecting said ignition, said timing control system comprising: crankshaft angular position detecting means responsive to the angular position of said crankshaft for producing detection output pulses indicative of a period during which the crankshaft rotates between first and second predetermined angular positions; and an ignition timing computing circuit including a plurality of individual computing circuits each thereof having: an integration capacitor; means responsive to said detection output pulses for selectively charging said capacitor during said period; a charging and discharging control circuit connected to said capacitor and responsive to first and second control signals applied thereto, said first control signal being indicative of an engine parameter, said control circuit including means for selectively initiating discharge of said capacitor in accordance with said second control signal and, means for varying at least one of the charging and discharging currents of said capacitor in accordance with said engine parameter; a capacitor voltage detecting circuit connected to said capacitor and responsive to the voltage across said capacitor for generating a discharge termination output signal indicative of said capacitor being discharged to a predetermined value; and said respective individual computing circuits being connected in a predetermined sequence, the discharge termination output signal of the just previous individual computing circuit in said sequence being applied as said control circuit second control signal to the next successive individual computing circuit in said sequence, said detection output pulses being applied to the first computing circuit in said sequence as said control circuit second control signal, and said discharge termination output signal of the last individual computing circuit in said sequence being applied as said ignition signal to said ignition means.