In motor driver, we need to use four pins: PIN1-Enable, PIN2-Logic Ground, PIN3-Half/Full Step, PIN4-Step Clock and PIN5-CW/CCW. In DI/DO, we use the first several Pins of PORT-A.
DI/DO---------Motor Driver
0------------------- PIN1
Power Ground ----- PIN2
1------------------- PIN3
PWM--------------- PIN4
3------------------- PIN5

The most important point is "PWM--PIN4", the commond is "W 50" to drive PWM, means the frequency is 50 Hz. The others can be found in Manual.