"conclude that 422 tends to be single pair half-duplex applications (whether multidrop or not) and 485 was dual pair full-duplex applications" duh
Just the opposite, 422 is dual pair 2 node full duplex, 485 is single pair multinode.

For information on serial communication 232/422/485 see http://www.national.com/apnotes/A...rface.html

Have fun,

Erik