I spent alot of time with Motorola concerning this subject exactly. Motorola does not support 3rd party developers mucking around with this port. I even accidentally picked up some internal technical terms and pretended to be an authorized field tech, but did not get anywhere. I was never able to get any feedback from the port and any random commands offered no response. I think that port exists only for specific in-house PC interface and command and control might not even be possible. Please let me know if you do get anywhere. I also have a feeling that the pinout is not standard, so first thing to check is to see if you can get RTS/CTS DTR/DCE voltages from any of the pins.

-Tom Visser