I am trying to choose a stepper motor controller for a 2 phase unipolar stepper, and I don't want PWM because I have limited PWM outputs on the microcontroller I am using. So I looked around and found stepper motor drivers that are controlled by an indexer and Serial(such as SPI). But I cannot find a satisfactory explanation of indexer control, so I would like to know whether or not the indexer step/dir control pins just work off of plain binary, like a 0 for clockwise and a 1 for counter clockwise, and a 0 for no movement and a 1 for "move one step"? I would also like to know the pros and cons of each control type.