Good morning Nghia,

Thank you for your question.

Since your PLC and PC are both DTE Serial Devices, to communicate between them you need to use a Serial Cross Over cable like the 1747-CP3, or a Serial Straight Through Cable with a Null Modem Adapter (Null modem cables and adapters cross or flip the wires going to pins 2 and 3)

But since the PanelView Plus and Plus 6 serial ports are DCE devices, you will a Straight Through Serial Cable to connect it to your PLC or PC via Serial ( you could add a null modem adapter on a 1747-CP3 to flip pins 2 and 3 again to make it a straight through cable.)

As far as DH-485, you'd typically add a 2711P-RN6 to a PVPlus or Plus 6 to get both DH-485 and DH Plus, and those can be picked up pretty cheap second hand.

Hope this helps,

Shawn Tierney,
Instructor at The Automation School