dhiraj_gehlot:
The stepper motor moves very fast when there is no acceleration. For acceleration, when the keeping the maxspeed to 6000, if the acceleration is 500 then motor moves very very slow. As I increase the acceleration, the motor rotates faster. However, the speed is very slow till the acceleration is below 6000. When the acceleration exceeds 6000, the motor start moving faster and after some value (~12000) speed saturates to a constant speed.
Without meaning to be unkind, that makes no sense.
If you have expressed yourself accurately then it seems to me the library is not working properly on your microprocessor.
The max speed of the motor should not be affected by the acceleration figure. The acceleration should only affect how quickly the motor gets to the max speed.
Can you try some suitable test code on a regular 16MHz Arduino and then see if the identical code gives the same effect on your super-duper MCU.
...R