The FLEX-6000 has a feature that allows for connecting either a serial or BCD connection from the radio hardware to third-party devices for passing band data and other limited other controls for selected devices.
How to do this is described in the USB Cable Interface Guide
http://www.flexradio.com/downloads/usb-cable-interface-guide-pdf/http://www.flexradio.com/downloads/usb-cable-interface-guide-pdf/