Abstract: A method and apparatus are disclosed for scanning a receiving medium (32) in an image processing apparatus (10) that allows a variable number of imaging channels, and printhead motion is provided by a lead screw (250) that is driven by a stepper motor (162). In one embodiment, the receiving medium can be mounted on a rotatable imaging drum (300). In order to advance a printhead (500) at the proper speed for a variable number of channels and to adapt the stepper motor for possible variations in drum rotation speed, encoder pulses from the imaging drum are divided by a programmed value to provide input pulses to a stepper motor controller circuitry at the proper rate. Pulses are counted so as to disable this input to the stepper motor controller after a pre-programmed maximum value is reached. Both the divisor value and the pulse counter value are variable, depending on the number of channels used.