vx2 port



I have ordered my ap 720 and been reading the install maual online. My question is witch port on the back of my vx2 should I use to recieve and send nmea0183 data. or is it necessay to use one port for recieving and one for sending. looking at the diagam for vx3 looks like port 3 but will that port recieve and send?
If you have a 10.4" NN2 (RDP149 or GD1920C) display, then typically customers use port2(wht/blk) to connect to TB6-3&4 to send AP instructions to drive the NAVpilot 720. In port setup on the NN2 Port2, turn on APB, GGA, RMB, RMC, VTG, XTE and ZDA. To receive NMEA0183 heading from the autopilot, use TB7-1&2 to connect to Data 3(wht/blk) on the 10.4" NN2 display. Once you have those physical connections, all that's needed is to enable HDG output from port2 in the NAVpilot 720 menu.
Thanks for all the help. Your knowlede of the product is appreciated.