In FULL mode the exhaust brake will engage any time when decelerating AND the rpm's are above 1200 AND the TC is locked. In AUTO mode the same rpm and TC requirements apply however it won't engage until the brake pedal is depressed (I've found just enough pedal to activate the brake lights to be sufficient) this allows coasting. Using tow/haul while in AUTO will bring in automatic downshifting while braking also.
If you need manuals you can go to ramtrucks.com and select the "owners" tab where you'll be able to DL them. You can also register on the site, enter your vin and find more information on your vehicle.
Peace