Does your device have the Modbus slave licence? My preferred Codesys plc has a Modbus master, but will not act as a slave due to not having the licence.
Some genius has probably written a Modbus slave library
Eaton Codesys doesn't need another license for Modbus slave
As normal standard Codesys V3 soft PLC, regardless your modbus master or slave, you have to do the configuration.
The step for configure as slave is adding the device->add modbus slave->add modbus serial device.
Then inside the modbus serial device have the memory where is for outside using reading holding register to read or write.
as for some other brand PLC like ABB, Wago , where default have open up the modbus slave function where will automatically to map all the PLC internal memory for all the modbus function.
this is example for standard codesys V3 softPLC modbus setup
Lee Junn Hei
Yes, I know these all things.
I've got answer from Eaton support, that the problem is with the Eaton Codesys.
So probably they will fix it in the next version.
Thank you guys for help. For now that's all. Bye