I built up my own micro-controller based on some reference books. The kernel was 8052. To increase the I/O ports, I attached the 8255 to 8052. Then, I attached one stepper motor to 8255. When I ran the assembly program, the stepper motor seemed to have constant speed. When I used my finger to touch the stepper motor, it seemed to vibrate on it own and I felt that it stepped discontinued. How can I make it to run more smoothly? In addition, how can I increase the speed of the motor? I want to ask one more question. What is the use of the crystal between the pins XTAL1 and XTAL2 of 8052? If I replaced it into higher frequency, then can I increase the speed of the motor?