Help: Stepper motor control with NI9401 and CompactRIO 9039

I want to generate the square waves to contorl the stepper motor through NI9401. And I have writen a simple FPGA code to generate the square waves as shown in Figure.

But now I want to generate finite steps for my stepper motor to move? How to do it?

Thanks very much!

English is my second language, sorry for my poor writting skills.