SDC21XX Ground Connections

I do not have the SDC2160 yet, but making plans to use it. I plan to wire the control power and motor power exactly like Figure 3 in the datasheet. My system will have 24V and GND. I cannot interpret from the datasheet how the grounds are configured internally. It seems that motor power ground and the IO Connector GND are labeled the same and therefore have straight connections internally. If I have the DOUT1 and DOUT2 sinking relay coil currents (~0.5A each), is that current directed to return through the IO Connector GND or the motor power GND? I am concerned about ground shift problems for sensors grounded to the IO connector. Can someone provide more detail about the internal grounding scheme, or proper external grounding/referencing of sensor signals to the IO connector?

The two grounds are connected internally. You should ground through the main power ground to avoid a ground loop.