From the RULES of using the MB-Master block:

A port which is to be used as Modbus master must not be used by Modbus_Slave . You can use one or several instances of Modbus_Master¹⁾with this port. But all versions of the Modbus_Master must use the same instance DB for the port.

You can only have one port open at a time, and all MB comms must use the same instance DB for that port.

I am not sure if this answers your question, but probably will raise more questions. 

The F1-help is very useful for these well established instructions.

Sanakiyen

Dear Experts,

I'm Working To Establish Modbus RTU Communication in CPU 1215 C-DC/DC/DC

In that, I have added "MB_COMM_LOAD" & "MB_MASTER" Blocks in to ladder network.

But, I want to configure the "MB_DB"  Port of the "MB_COMM_LOAD" Block.

As per Forum users (Documentation & Examp.. ) Its addressed As A word tag Should be Created in   Auto Generated "DB" of "MB_MASTER" block.

But, The Dada Block (DB) is Write Protected. I Couldn't Push Values on that Block.

Details are shown by images.

Kindly help me on What need to be addressed in "MB_DB" Port. And,How can i do that?