Driving sequences for stepper motors

If you can get a copy of the January 1994 issue of Embedded Systems Programming there is an excellent writeup on driving stepper motors using an 'hc11. Basically what he describes is a unipolar drive that is driving a 200-step motor. The unipolar drive utilizes 4 MOSFETs, each driving on of the four windings of the motor.

Full-stepping sequence

STEP    Q1      Q2      Q3      Q4
1       ON      OFF     ON      OFF
2       ON      OFF     OFF     ON
3       OFF     ON      OFF     ON
4       OFF     ON      ON      OFF

Half-stepping sequence

STEP    Q1      Q2      Q3      Q4
1       ON      OFF     ON      OFF
2       ON      OFF     OFF     OFF
3       ON      OFF     ON      OFF
4       OFF     OFF     OFF     ON
5       OFF     ON      OFF     ON
6       OFF     ON      OFF     OFF
7       OFF     ON      ON      OFF
8       OFF     OFF     ON      OFF