ClassicLadder modbus RTU slave

Because can facilitate a lot ... on old post someone talk to me about possibility to set modbus RTU on classicladder as SLAVE of other master Modbus serial ... these for exchange data from an old pc to my classic ladder program Lcnc .... someone have these experiences ... because not see how can. Using "set ID slave" text box with "0" value or leave it black?

Or not possible at all?

regards

Linuxcnc / Classic ladder manual for Modbus section 9 linuxcnc.org/docs/2.5/html/ladder/classic_ladder_fr.html Linuxcnc wiki wiki.linuxcnc.org/cgi-bin/wiki.pl?ClassicLadder_Ver_7.124 I don’t think Linuxcnc/classic ladder has a Modbus slave RTU built in.If you know bit of C language you can try writing your own user space Modbus RTU slave protocol using libmodus driver. Search internet and GitHub for examples to help you write the Modbus RTU slave communication protocol. libmodbus.org/  

These my request is based on an old reply came from a developper ... at that time not try to do because use my ethernet comp.

regards