I did something similar about 15 years ago; a DC setpoint input signal (0-5V) was fed into an A/D convertor; the resulting 8 bits formed the address lines of an eprom. The output byte from the EPROM was then passed to a D/A convertor whose analogue output was compared with another (0-5V) signal from the centre-tap of a potentiometer linked to the motor's shaft. Some LLS TTL logic determined the direction and fed pulses to the stepper to move in the direction to null out the voltage difference across the comparator inputs. The voltage references for the A/D and D/A were connected together and fed from 1/2 Vcc. The whole thing performed well - changes in Vcc did not affect accuracy/repeatability. I was able to store different profiles in the eprom. The stepper shaft had to rotate over 180 degrees for the 0 to 5 volt span. Using a precision pot with approx 270 degrees rotation (no mechanical stops) allowed for adjustment at either end of the span. This design didn't actually use a micro-processor! It would be relatively easy implement this on the 8052.