I just did a project using a PF 753 that I was controlling via Ethernet IP. Ken Roach has posted several ideas about how to best control a PF via Ethernet IP.
Basically, to start the drive set the LogicCommand_Start bit to 1 until the DriveStatus_Running is true. Set the Reference to the RPM or Hz you want.
To Stop the drive set the LogicCommand_Stop bit to 1 until the DriveStatus_AtZeroSpeed bit is true. I also move a 0 into the Reference.
This method has worked perfectly for me. Good Luck.