The board has three isolation domains with separate ground returns: logic (GND: controller, USB, RS-485, encoders, analog inputs), motor (MotorGND: drivers and motor supply) and field I/O (Opto GND: digital inputs and outputs, limits, home, latch). The domains are separated by optocouplers. 

Connector locations and panel labels 

Figure 3. Connector, jumper and test-point locations (board top view, front panel at the top). Colors show the isolation domain 
● marks pin 1 as numbered in this data sheet.