Abstract: Improved drive logic for a stepper motor is provided using a closed loop feedback system which includes a coded disk driven by the motor and decoding means to derive signals from said disk. The motor is operated at varying speeds in accordance with variations in the lead angle between the energized motor windings and the motor shaft position. Motor drive signals are generated in response to the sensing of leading or trailing edge pulses from the coded disk, and the lead angle, and thus the speed of the motor, may be increased or decreased by selectively shifting the control of the drive signals from a pulse leading edge to a pulse trailing edge or vice versa, thereby providing a change in the lead angle. In addition, pulses from the coded disk may be blanked in order to effect a decrease in motor speed.