Whichever block you are receiving the status output of 7001, that is a common status value for comm blocks.  For the other, you need to click on the block producing 16#8281 and press the F1-help, and then start scrolling down to find the status codes.

What types of codes are shown?  For certain the 16#7001 code is shown, and I imagine the 16#8281 is also shown.

Are you using something like this right after calling that block:

IF MB_Send_Error THEN Saved_MB_Send_Status := MB_Send_Status END_IF;

That's the best way to capture ERROR values.  16#700x values are typically not ERROR values.

Weaver1950

Dear all,

I am trying to establish a connection between the s7-1200 PLC and the Imeon 9.12 Hybrid inverter. I use Modbus RTU protocol with RS485 on the physical layer where the PLC is master and the inverter is slave. I am trying to achieve this with the Modbus_Comm_Load and Modbus_Master functions. In the Modbus_Master function I get errors 7001 and 8281 alternately. Can anyone tell me what these errors mean since they are not explained in the Siemens documentation.

Thank you in advance!