I-O Display Systems Basic I/O Product - Manual (Page 58)

Installation 2
2-4(Vol.2)
RS-422:
Advantages: Easier to implement in software since host driver need not be controlled.
Can be either Multidrop or Repeat.
No turn-around delay required.
Disadvantages: Requires five conductor wire instead of three.
RS-485:
Advantages: Needs only 3 wire conductor.
Disadvantages: Host 485 driver control must be implemented requiring tricky serial port
manipulations.
Can only be Multidrop.
Usually requires turn around delay implementation.