You need to be more specific about what you want. I can design lots of different configurations of keypad, A/D, DAC and stepper motor. What are your requirements?
For example:
8,10,12,16,24 bit DAC? How many channels?
Use the on boad A2D or External A2D?
If internal, how many channels?
If external A2D then 8,10,12,16,24 bit A2D? How many channels?
What kind of stepper motor? Unipolar or Bipolar? What Voltage? What Current? How much holding torque? What is the maximum speed? How much inertia in the load?
What kind of keypad? membrane? spring switch? other?
Which flavor of the AT89C51 did you have in mind?
I've used the CC01, CC03, and ED2.
It will be a great help to both of us if we can clearly see what "done" means.