Hi,

I’m working on an old project with an S7-300 CPU 314 that was developed in TIA Portal v13. The client now needs to retrieve alarms from our PLC using Modbus RTU slave communication over an RS485 interface.(8bits,one stop bit ,none parity, data Hex. word)

To facilitate this, I’ve added a CP-341 module and a Modbus slave dongle (hardware only). In the program, I called FB80 from OB1 and created a data block to hold the alarm data. I also specified this data block number in the P_SND_RK block.

Could you please review my approach? I have limited experience with this, and any guidance would be greatly appreciated. I’ve also attached a screenshot of the data block for your reference.

Closed because posted twice. The active topic can be found here:

Retrieve alarms from PLC using Modbus RTU slave communication over RS485

Kind regards, Moderator_Lan