Modbus communication?

Projects Interfacing w/ Software on the Computer
1

Hello all, I need to get temperature data from control temperature and I have problem How to use arduino communicate with Temperature control (dixell XR20CX) by Modbus interface

Communication detail

modbus RS485 RS232
control temp -----------------> XJ485-CX ----------------> Interface to RS232 ------------> Arduino
(dixell XR20CX)

Information

  1. dixell XR20CX use Modbus RTU ecd dixell 2019

  2. I can use dixell XR20CX interface to PC by Modbus32 software and got temperature
    Device ID :1 Address: 257 Range:1 type Holding Register (type I'm not sure)
    RS232 baudrate 9600 Length 8 Parity NONE Stop bit: 1

  3. I think should use example from http://sites.google.com/site/jpmzometa/arduino-mbrt/examples
    I need help modify code for get data address 257 rage1 only

Thank you.