I did not work with Motoman controllers, but I did work with other robots, Modbus and DeviceNet.
Modbus TCP is probably the easiest to use from the client side. On the DX100 Side you need to check which modbus address coresponds to the functionalites you would prefer. If you want to move the robot along the X axis, you need to check in the documentation which Modbus register(s) you need to write to make the robot move. (Please note that since I do not know the Motoman controller it is not sure that moving the robot via modbus is possible.)
After you have identified the needed registers, you can connect a freely available modbus slave (or master, depending on configuration) running on a normal PC to see if the robot moves when you write the registers. You can find a number of programs capable of doing this here.
I assume it is needed that the robot is not connected to a PC but to a PLC via Modbus. If you have correctly identified the required registers via the PC software, you can cofigure the PLC to do the same, read/write the required Modbus registers and you are done.