The Part number for the "dongle" is W05-0611-00, Data Connector
In the TS 480 service Manual, it says that pins #3 And Pins #6 are "shorted.
Look at the Picture below. ( if you click the picture, let it load, and click it again, it will load in 100% size)
This describes how to build the cable
Part number W05-0611-00 data connector.
I have not verified this so proceed with caution, I do not have the radio to try it on.
Let me know if you have the service manual, you will need it.
73
Jeff