The stepper motor have to be driven by unipolar driver so only a 5-wire or 6-wire stepper motor may be used, as shown below:
Note that using the sequencer to drive the stepper motor is only meant for very low speed operation and you can't do much to control the acceleration and deceleration. Also STEPMOVE, STEPSPEED commands do not apply to this.
A new F-series PLCs that scheduled for official release around first quarter of 2009 features 3 channels of built-in stepper motor drivers that is controlled by the STEPMOVE and STEPMOVEABS comamnds. Stay tuned for the announcement.