CPU 314 and ET200S as Modbus Slave

Hi everyone,

I have a doubt about the configuration of an ET200S module as a modbus slave.

I have a CPU 314C 2PN/DP (6ES7 314-6EH04-0AB0) connected via profinet to an ET200S interface module IM151-3 PN (6ES7 151-3AA23-0AB0), on the ET200S I have a PM-E power module (6ES7 138-4CA01-0AA0) and a serial communication module modbus/uss (6ES7 138-4DF11-0AB0).

I have to set this communication module as a modbus slave so that with a master modbus DCS I can read and write values in the PLC.

In the hardware configuration I have already created the profinet system where I inserted the interface module, the power module and the communication module (taking from the catalog the one that says "1 SI Modbus Slave 8 Byte").

Then I went in the module properties and set the parameters (speed, address, ect).

After this, from this address Modbus Example I downloaded the example program and the manual (also attached to this message).

According to the manual, to set the module as a modbus slave I have to use only the function block FB81 with his instance block DB81 and the conversion block DB100.

I call the FB81 and parametrize the DB81 in the main (OB1), then in OB100 I set the merkers for starting the communication and in DB100 I set which DB will have full access by modbus (I will use modbus function code 3 and 6).

Since this is my first time setting up a modbus communication with an ET200S, I'm asking to someone that already made a modbus communication with ET200S if these steps are correct or I missing something.

Thanks for the help.

P.S.

The manual also says that FB81 make an internal call to FB2 and FB3.

But aren't FB2 and FB3 used only if I have to set module as a master?

If not, then have I to insert them in the program even if my module works as a slave?