The 32i doesn’t have an Ethernet port so I’ll assume you mean the T3-22i.
In this screen shot below we have a T3-22i connected on the RS485 subnet and it shows in the inputs screen as external inputs, this is fully transparent and requires no setup. Exansion I/O is not normally be used on the Ethernet port as expansion i/o in our T3 environment at least, since that’s the way our system grew up.
If you had an application that called for adding expansion I/O using the Ethernet connection you can do that too but its not as flexible. You would need to read/write all the registers or bacnet objects manually in a program. For Modbus use the REG keyword command or in Bacnet use the AV,BO,BI,AO commands. Here’s an example of using those commands when integrating a Honeywell SmartVFD using bacnet, it would be the same in Modbus except you’ll use the REG commands to read/write Modbus registers.
https://forums.temcocontrols.com/t/programatically-updating-a-honeywell-smartvfd-with-t3000/120
The T3000 front end makes it a lot easier to manage the expansion i/o when its connected using RS485 and set to Modbus protocol. Soon bacnet mode will be fully transparent as well.
