The people who use to work with Delta analog I-O modules, use to have the same doubt.
Why the engineers put a RS485 port on analog I-O’s if you use internal bus to communicate with them?

The reason is very simple, our analog I-O’s can work trough the internal bus, but can work too trough RS485 communication too.
So, with that feature, is possible to create a remote analog I/O’s without any other device.
Just as a reminder, if you need to add digital I/O’s to your, then you should have to add the RTU-RS485 module to your distributed network.

The process to configurate the network is not difficult, but you have to go step by step.
1. The first step to configurate the RS485 protocol into the analog module, is runing the following example, who is ready to communicate with the PLC at ASCII 9600 7,E,1.
DVP04TC RS485 config communication.dvp
If you are interested to know how I did it, go to the Analog Control post

2. Once the protocol is configured, you can double check with the Extension Module Wizard and some IFD6500 (USB to RS485 converter) connected to our computer.

3. Finally, to work with them trough RS485, you just have to communicate with the analog module as an Inverter or temperature controller, or any other RS485 based device.
Remember:
To Write
MODWR “Station Address” “CR number” “Number of data to be write”
To Read
MODRD “Station Address” “CR number” “Number of data to be read”
And SET/RST teh M1122 to trigger the command

Check the following example for better comprehension
DVP04TC RS485 Read-Write.dvp

name: den-eindhoven
Password: BuPd2175