485 4 wire to 2 wire connection with PCIe 8431

    I am trying to connect to a watlow temperature controller with my PCIe 8431.  When I wired up the cable I shorted Tx+ to Rx+ (p 4,8) and Tx- to Rx- (P5,9) to connect to the controller.  I assume this is converting from 4 wire to 2 wire but, when you look at the "loop back" connections from NI this is exactly what they tell you to do.  I ask since I am uncertain and I am not able to establish communication with the controller.