Dear Expert,

I am trying to setup communication with TIA PORTAL V13 Sp1 with the MB_CLIENT. I am making two calls, one with mode 0 (Read) and one with mode 1 (write).

Read: Mode = 0, ID = 1, Connectiontype = 11, ActiveEstablished = true, remote port = 502 and local port = 502

Write: Mode = 1, ID = 2, Connectiontype = 11, ActiveEstablished = true, remote port = 502 and local port = 502

I also have tried to change the local and remote port to 503 (first on the read instruction and then also on the write instruction).

The problem is that at the write instruction I am getting an error 80C4. In order to make sure that one call is not interferring with the other call I set REQ of the read instruction to false but no change (still error 80C4). I also tried to disconnect the connections with TDISCON and establish the connection again with no result. When I try to read and write with a modbus simulator reading and writing is no problem. When setting up communications again I can make it work with the write instruction but then I am having errors on the read instruction. So both at the same time (eventough the call is not active at the same time) seems not possible. What also puzzles me is that even when REQ is false the status is changing all the time and also the error output is going on and off. Suggestions will be much appreciated!

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Split from Sample Program: Modbus TCP with S7-1500.

How many remote devices are you communicating with?

How many connections are you creating using TCON?

If you are connecting to one remote device and use one TCON, then ID is the same for all mb_client calls.

You can use the same connection to the same remote device for reads and writes.

If you have multiple TCONs that are successfully connecting, the remote ports can be the same, but the local ports must be different. 

JaZa

Dear Expert,

I am trying to setup communication with TIA PORTAL V13 Sp1 with the MB_CLIENT. I am making two calls, one with mode 0 (Read) and one with mode 1 (write).

Read: Mode = 0, ID = 1, Connectiontype = 11, ActiveEstablished = true, remote port = 502 and local port = 502

Write: Mode = 1, ID = 2, Connectiontype = 11, ActiveEstablished = true, remote port = 502 and local port = 502

I also have tried to change the local and remote port to 503 (first on the read instruction and then also on the write instruction).

The problem is that at the write instruction I am getting an error 80C4. In order to make sure that one call is not interferring with the other call I set REQ of the read instruction to false but no change (still error 80C4). I also tried to disconnect the connections with TDISCON and establish the connection again with no result. When I try to read and write with a modbus simulator reading and writing is no problem. When setting up communications again I can make it work with the write instruction but then I am having errors on the read instruction. So both at the same time (eventough the call is not active at the same time) seems not possible. What also puzzles me is that even when REQ is false the status is changing all the time and also the error output is going on and off. Suggestions will be much appreciated!

Hello Huggy_d1,

Thank you for your help. I only have one remote device where I am communicating with. I also have just one connection created with TCON, in the meantime I removed the TCON instruction, the connection is buildup bij the MB_client itself. I changed the program by using just one ID (No. 1) as you suggested but no result. Please take a look at the attachments, there is not more in the plc then these networks. As you can see REQ is false at both MB_Client instructions however in NW2 it seems to be active (green border) and in network 3 it's not. Even tough REQ is false at the write instruction (network 3) there is an error and status 16#80A3. I hope you have another suggestion. Thanks for helping!

Jan

Hello Huggy_d1,

Thank you for your help. I only have one remote device where I am communicating with. I also have just one connection created with TCON, in the meantime I removed the TCON instruction, the connection is buildup bij the MB_client itself. I changed the program by using just one ID (No. 1) as you suggested but no result. Please take a look at the attachments, there is not more in the plc then these networks. As you can see REQ is false at both MB_Client instructions however in NW2 it seems to be active (green border) and in network 3 it's not. Even tough REQ is false at the write instruction (network 3) there is an error and status 16#80A3. I hope you have another suggestion. Thanks for helping!

Jan

 You need to make the disconnect true to completely close the req. Only then it closes. Also you may need to check the MB UNIT ID and set is as 1. And you need to reecompile all the whole Program blocks. Not just download option. Compile the Software and then download.

Also verify the Modbus device is communicating using some PC software like Modscan or Modpoll or something.

Thanks,

Jay

JaZa

Hello Huggy_d1,

Thank you for your help. I only have one remote device where I am communicating with. I also have just one connection created with TCON, in the meantime I removed the TCON instruction, the connection is buildup bij the MB_client itself. I changed the program by using just one ID (No. 1) as you suggested but no result. Please take a look at the attachments, there is not more in the plc then these networks. As you can see REQ is false at both MB_Client instructions however in NW2 it seems to be active (green border) and in network 3 it's not. Even tough REQ is false at the write instruction (network 3) there is an error and status 16#80A3. I hope you have another suggestion. Thanks for helping!

Jan

Hi JaZa,

I just struggled with the exact same thing.

My S7-1500 is Modbus Client, and I need to read (FC03) and Write (FC16) holding registers to ONE Modbus Server/Slave. At first I did what you tried, using two MB_CLIENT blocks with different Connection ID's. I made it work by triggering REQ and DISCONNECT etc on and off, but I wasn't happy with the result. I kept thinking it has to be a better way. (I wanted to avoid CONNECTING and DISCONNECTING all the time to eliminate stress on the Modbus link).

I found a nice solution here at the forum that works great! It is created by Siemens expert Mr. Denilson Pegaia. Link to the forum post here:

https://support.industry.siemens.com/tf/ww/en/posts/sample-program-modbus-tcp-with-s7-1500/98690?page=3&pageSize=10

Download his sample program called MODBUS.ZIP posted on 4/28/2018 3:38 PM. Link here:

https://support.industry.siemens.com/tf/ww/en/postattachments/download/?attachmentId=101943

He created a toggle logic between reading and writing, using the same MB_CLIENT and same Connection ID. The trick was to use the EN input on the MB_CLIENT block.

I suggest you download the sample program and see. You have to enable CPU clock memory bits, and then you can decide how often you want to poll for new data using the different bits.

Good Luck!

Edit:

Just realized that you are using V13, so you will not be able to open the sample project.

So I've attached a PDF showing OB1 and the Datablock you need. Hope it helps!

BR,

Ole-Jacob Sørensen

Hi Jay,

I did follow your suggestions but that wasn't the solution. I also transfered messages with modbus poll with two instances of modbuspoll at the sametime (reading and writing) without any problem. However the problem is solved now with the solution of olejacosor (see my response there for details). Thank you very much for helping!

regards,

jan Zandvliet

Hi Ole-Jacob,

I have been out of the office and therefore I couldn't try and answer your solution before. I have tried it now and it's working flawlessly! At first I dragged and dropped de MB_CLIENT blocks into the program and have the two instance DB's generated but then it was still comingup with errors. Then I noticed that the same instance DB was  used for both MB_CLIENT blocks, after this change it's working beautiful! Thank you very much for thinking and your help.

Note:

After the first time there was an error on the MB_Client, when i changed the program it did not recover from the error, then I toggled the "disconnect" input but the error stayed. Only when I switched the cpu to stop and a restart the error disappeared and communication was o.k.

yours,

Jan Zandvliet