As will be noted in the attached Wireshark trace I have successful Modbus TCP communications between my S7 1200 (212-1BE40-OXBO) Client and my Modbus TCP Server (Modbus Slave).

The problem I have however is that the slave ID is 255 and I wish to use ID 1. I've read two Siemens white papers on the subject but I'm unable to deduce where the slave ID is set.

The attached also depicts my config.

Is this a 'school boy error'?

Thanks in anticipation!

Hello,

look to instance DB of block and check MB_Unit_ID Tag. This is your solution.

Many Thanks!

Found the MB slave ID as per your recommendation!