XXMIT Instruction & Modbus Communication

XXMIT Instruction & Modbus Communication Once again on XXMIT Instruction,i am using CPU 434 12 and concept 2.6, Do i have to purchase XXMIT Loadable(Instruction)
as it was not there with other PLC's of quantum Series.if yes then how much it will cost......
Furthermore i am planning to use modbus ethernet gateway which will avail the facility to communicate with out XXMIT. In this case also (I think)I have got three options for PLC to Gateway communication 1)using MSTR Instruction 2)using ethernet I/O Scanner
3)using CREAD_REG CWRITE_REG
am i right.......?
Waiting for a detailed answer
Thank you in advance.

You only need the XXMIT function when you are using one of the serial ports on the processor.

If you are using ethernet then consider the READ_REG/WRITE_REG commands. The MSTR can be used but it is really intended for 984LL programs.
The Ethernet I/O scanner is only good for other Schneider devices that support I/O scanning.
The Cxxxx_REG commands are continuous read/write communications where the xxxx_REG commands are event driven.