It depends on what hardware you have available between the stepper motor and the 8051. If you have a "translator" module that takes step and direction signals as input, you can provide timed step pulses and a static direction signal. If you have simple solid state switches and no translator module, then you can control them directly in the proper sequence. You will need to know if the stepper is bipolar or unipolar. Assuming a unipolar connection with four switched to ground and a motor common connected to the power supply, a full-stepping sequence would be 0011 0110 1100 1001, etc. A half-stepping sequence would be 0001 0011 0010 0110 0100 1100 1000 1001. If the motor is bipolar with two windings that can be energized in two directions, a full-stepping sequence would be ++ +- -- -+ and a half-stepping sequence would be 0+ ++ +0 +- 0- -- -0 -+ (where 0 means off). As you can see, a translator really makes things easier.
