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Split from Open Modbus TCP/IP communication.

Hello,

ENQ_ENR = FALSE, and that's the problem. There's only one error displayed - and this is A090 (missing license code). I've even tried to check Simens's MODBUS_PN_CPU_EXAMLE from a sample projects, stil I have absolutely the same result...

And there's one more thing confusing me is that my cpu simulator won't ping.

Hello,

Can you try with attached code? or you can compare with your code

Use the S7300 client code in attached program.

A090 is ok, because you don't have license so SF LED  will flash. 

S7 300 Act as Client(192.1680.1) and Modbus  Server(192.168.0.200) and port number 2000

You need to enable DB1.DBX12.1 to receive data from Server.

DB1.DBB68 as Unit ID =1

Data Type is your function code

Start address

Length and Read or Write Bit (0 or 1)

You will find detail in Client as variable table of sample application.

Also you can use Modbus TCP wizard to create connection.

https://support.industry.siemens.com/cs/in/en/view/60735352

Thank you for your example!

Unfortunately, it does'n work either. I've downloaded both CPUs to simulators.

When I'm setting ENQ_ENR=TRUE on client side, nothing happens. I've set MODBUS_PARAM data block according to manual S7 OPEN MODBUS / TCP Communication via the integrated PN interface of the PLC, and even tried to set it through Modbus TCP Wizard, and got absolutely the same result.

I attached the screen of Var tables I'm working with. Could you take a look at it?

By the way, why do you use 2000 port for modbus server, should'n it be 502?

Thank you!

Hello,

Same sample should work without any issue. I have just tested. You can use either  502 or any other which is free port in PLC. i have used 2000. Some of the server its fixed as 502.

I can seen in screen shot of VAT, you are using function code 3 which is for Holding register and having length 5 with mode as write.

So it means you are writing 5 holding register from Client to Server.

Write some values in holding register of client so you can see same can be available in server holding register DB or not.

You need to only trigger Request bit at client. Keep Request bit high at server.

Still if you are not able to do it, tomarrow i will make video for it and post it here.

Hello,

Congratulations, finally u did it.

Yes, both server and client having same IP becuase i was using common PLC to test as Modbus TCP as well as Modbus TCP server function.

Once i defind PLC as client (192.168.0.1)that time i was using Modsim(192.168.0.200)as mobus tcp server simulator software for testing.

And while server testing , i defined PLC as server (192.168.0.1) and Modscan (192.168.0.200) as client , again its simulator software.

I didnt do PLC-PLC communication via modbus server client blocks thats why its same IP in project with common CPU.

Hello! 

I've got another question about Modbus. We have redundant pair of CPU 412-5 H PN/DP, wich suppose to connect with third-party plc over Modbus TCP through CP443-1. I've parametrized CPs as Double-sided Server. Now, is it possible to simulate these CPs (at least, one of them) in order to test the connection with Modscan? If yes, how?

Thank you.

Hello,

Again its depends on ur partner.

If partner is also redundant modbus tcp client then little bit difficult. You need to use two Laptop as modscan client.

But partner is modbus tcp client single connection then you can use ethernet switch between two cp and modscan pc.

One more possibilty you can check with TP comfort panel as modbus tcp client .

For testing , you can use one counter with 500 ms increament and check with both cp output continously.