I am trying to configure a simple Modbus RTU message and I am getting an error status of 16# 8281 on the Modbus Master block.  I have searched both the forum and the S7-1200 manual, but I cannot find this error code.

I attached the program.  Does anyone see what I am doing wrong?

Thank you in advance.

I've re-selected the port and also tried entering the port number in HEX, both with no success.  I did notice that the folder with the new Modbus blocks(Communication Processor --> MODBUS (RTU)) contains a mix match if block versions.  The Modbus_Comm_Load block is version V3.0 and the Master and Slave blocks are V2.2.  

Could this be the problem?  I don't think you can use blocks with different major revision together.  Did Siemens not provided us with the V3.0 Master and Slave blocks? Or an I overlooking them?

See attached screenshot.

Saint Germain

I've re-selected the port and also tried entering the port number in HEX, both with no success.  I did notice that the folder with the new Modbus blocks(Communication Processor --> MODBUS (RTU)) contains a mix match if block versions.  The Modbus_Comm_Load block is version V3.0 and the Master and Slave blocks are V2.2.  

Could this be the problem?  I don't think you can use blocks with different major revision together.  Did Siemens not provided us with the V3.0 Master and Slave blocks? Or an I overlooking them?

See attached screenshot.

 Hello Saint Germain.

Did you solve this problem? I am having the same problem.

Regards Ari

Hi Ari,

I was not able to get the V3.0 Modbus blocks located in the MODBUS (RTU) folder to work, but I was able to get the V2.2 Modbus blocks located in the MODBUS folder to work.

Hi ,

I also faced a problem when i was unsing the Modus RTU blocks V3.0

My problem was fixed when i changed the Static parameter Mode to the value 4 in the Modbus_Comm_Load_DB. The value 4 means that you are working with the Modbus protocol.

To be shore i move the value 4 to the " DB Modbus_Comm_Load_DB . Mode " at First Scan.

I hope this was helpfull.

Greatings

Dear Saint Germain

This is regarding Error (Status) 8281 Again.

In your last conversation you havent updated weather your problem has solved or not??

As i am getting same problem,implemented remedy suggested by "Sion"..

""""    

Hi ,

I also faced a problem when i was unsing the Modus RTU blocks V3.0

My problem was fixed when i changed the Static parameter Mode to the value 4 in the Modbus_Comm_Load_DB. The value 4 means that you are working with the Modbus protocol.

To be shore i move the value 4 to the " DB Modbus_Comm_Load_DB . Mode " at First Scan.

I hope this was helpfull.

Greatings""""

Still My problem is not solved.Please help.

Hello,

really not enough infos with which instruction you have this error status, but try look for first if you have correctly defined MB_COMM_LOAD parameters, especially port of CM/CB card. This error can point to this. Reconfigure/download/Init better OFF/ON PLC, because most of users put init MB_COM_LOAD to OB100. If you'll have correct true output from MB_COMM_LOAD status bit DONE, then initiate MB_MASTER instruction.

Hello,

Are you using S71200 or S71500 PLC?

If you have S71200 with it's own Communication module, then use the Modbus library V2.2 from Modbus folder not from modbus RTU folder.

You need to use library from Modbus RTU folder having version 3.0 is only when if you want to use CtP module of ET200SP with either S71200 or S71500 for modbus RTU application

That time you need to define the mode as 4 for RS485 interface with 2 wire output modbus.

The error saying that check the port.

Can you post your code screen shot?

see the attached snap shot MB_Comm_Load block.

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