Hi,

My customer using S7-1200 CPU1214 with TIA V13 Sp 1 and using MB_Client V3, reading information from third party power meter. Some problem occurred when they connected to 9th....more devices. Not sure the maximum number of Modbus Server devices?

Please advise?

Rgds,

Chantid B

Denilson Pegaia

Hi,

Here there are a sample project and some tips for implementation of MODBUS TCP with S7-1200:

1 - Pre requisites: STEP 7 >= V11 SP1 and S7-1200 FW >=2.1

2 – Documentation: the help on line of the blocksMB_SERVER and MB_CLIENTare the best way to get information about these blocks.

3 – Programming:

3.1 – On MODBUS TCP server

Use MB_SERVER instruction on the server:

Ports: as default you can use 502, however it is possible to use any ELSE ports already
used by S7-1200 (20, 21, 25, 80, 102, 123, 5001, 34962, 34963 and 34964).

Each connection needs a block call (with different instance DB, ID and port)

3.2 – On MODBUS TCP client:

Use MB_CLIENT instruction on the client:

Each connection need a block call (with different instance DB). ID and port must match with the server).

4- Status 7002 = meaning that there is no client connected.

 

 

NOTE: As from CPU FW4.0 / STEP 7 V13 SP1, the blocks MB_CLIENT / MB_SERVER was changed.

Now they are similar to S7-1500. The main difference is that now the connection definition is not made in block inputs but else in a external place (DB).

 

To create the connection reference DB, create a DB as usual, and as variable (any name) you should type (manually) as data type “TCON_IP_V4”.
The blocks online help shows the meaning of the variables.

I attached now two examples at one zip file: one for FW>4, other for FW<=3 (as original)

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Split from Tips and sample program for MODBUS TCP.

Hello ,

The way i do is :

1. Create a pulse for (500ms / 1 sec. ) as per your req.

2. Create a up Counter.

3. on counter =1 , call first Modbus device. and so on till "n" device. 

4. When you reach the last counter then reset counter and the cycle will again continue.

Also have a look at the below link :

https://support.industry.siemens.com/cs/document/83130159/how-do-you-program-and-parameterize-modbus-tcp-communication-between-two-s7-1200-cpus?dti=0&lc=en-WW

Thanks,

Pratts23.