Dear Customer.

If a modbus master query to non existence address in modbus slave, 

modbus slave will return 'illegal address'  because address query from master doesn`t exist in modbus slave.

so you better input address using virtual status point or analog point.

Or If you check 'ignore illegal address', modbus slave will return empty value(0) when master query about non exist address.

here is manual link (ModBus TCP/RTU) ,I hope you ask your Korean colleague.

Thanks

------------------------------------------------------------- 

Dear Anygate,

I have some points set to be sent over modbus using the modbus virtual device. However, using external software (Modbus TCP view), I am only able to read the points in the address range of ~600-650, but the points in the range of 800 result in "invalid data address" error. How can I fix this?

Thank you,

RPE