An electric motor drives a belt spool of a seatbelt retractor in a vehicle using a micro-controller and a drive circuit that drives the electric motor. A plurality of PWM control signal sources are provided each of which has a trigger input and a control signal output. Each control signal source, upon application of a trigger pulse to its trigger input, provides on its control signal output a control pulse of a duration different from durations of control pulses of all other control signal sources. A set of motor control programs are permanently stored in the micro-controller. A program selection signal is sent to the micro-controller from a central sensor unit in the vehicle. Trigger pulses are sent by the micro-controller to the trigger inputs of the control signal sources. Particular ones of the control signal sources are selected for application of their signal outputs to the drive circuit in a control sequence defined by a selected control program.