T2016P Modbus connection

Hello all. I need some help setting up a Modbus connection with a Carlo Gavazzi T2016 controller. The controller is being used to control our compressed air pressure in the plant. I want to be able to alter the setpoint with a DL-06 PLC. I followed the cabling instructions and am getting blinking TX and RX lights on the PLC. I setup the secondary com port on the DL-06 as RS485 2-wire 19200 baud Modbus protocol and address 1. Attached is the spec for the T2016 Modbus. I have tried an MWX to change the setpoint but no luck. I am writing a value from register V2200 to address K4128. (The setpoint address is 007F, so I converted it to decimal and added 1 to come up with 128).

Any advice is welcomed.

www.carlogavazzisales.com/usermanuals/CGIModbusGuidev110.doc

Still trying this morning, but no luck yet.

Any advice?