Anyone can tell me why my servo motor can only in one direction.

When i run mach3, it moves in one direction and then stop and then the same direction. Whenever the Axis drops value, the motor stop. It should be turning opposite direction, but it doesn't. Why? Can anyone tell me pls...

Another question how does mach3 knows i am using servo or stepper motors? How does it configure the output and motor signals?

                     

Mach doesnt know or for that matter care whether you are using servos or steppers. All it does is put out Step and Direction signals to the drives.
 Check you have the Dir pin and port set correctly.

Hood