Look up table Calculation for Modbus

Hi to All,

I m new in Modbus. I want to know that how to make or get the Modbus Lookup table for communication between two PLCs or you can say between PLC and DCS.

If i have I0.0 at Siemens plc as a Digital Input, then what will be its Equivalent Modbus address which i would call at Master PLC or DCS for writing or reading whatso ever.....?

Same as i have a data in Data Block like DB1.DBW0 then what would be its equivalent modbuss address....?

Thanx in advance.

Regards,

Hello ahsen;
There is no one-to-one conversion table for Modbus registers and Siemens S7 registers.
Everything depends on the parametrization that you decide to setup in your master or slave program (in the S7 CPU). For example, ypou decide which is going to be your Base Register (start addtess) for a specific Modbus Function; then everything is calculated based on offset and ranges ...
Actually, it is more critical when you are setting the S7 PLC as a Modbus slave.
Have a look at a recent discussion on another forum, look up the attachments and study the proposed manuals, they should help you clear the issue out.
https://www.automation.siemens.com/...ow.aspx?HTTPS=REDIR&PostID=219148&language=en
Hope this helps,
Daniel Chartier