Garmin Fleet Management Interface?

There's a company called Argent Data that I occasionally have contact with. They sell a cable, meant to get NMEA data from several Nuvi models, including my Dezl 560LMT. I don't have that cable, but the guys at Argent tell me it puts the GPSr in the FMI mode.

If you're looking for more information, they might be able to help.