I've been working with this type of robot and controllers, and usually they come (here in Europe) with 8 inputs and outputs in the arm, and then 16 input and output inside the controller. You can change the arm outputs and inputs from NPN to PNP or viceversa via a switch, but the inputs and outputs inside the controller are just PNP or NPN. But there are too many options as RussB said, so you'd better ask the supplier.