Dear all

I have a problem with MB_MASTER block of PLC 1200. I using s7-1200 communication with  relay 7SJ80.

 Sometime  I only getting the BUSY flag, not getting DONE or ERROR flag or any messages. But if I STOP and then RUN PLC  then everything seem like OK. 

I am attach my program

Kindly help me solve the issue.

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Split from S7-1200 Modbus Communication Problems.

Hi There

I have the same problem.

When I stop and run again PLC, everything is OK and I have communication for a couple of hours but suddenly communication lost and master (1200) stay in busy mode.

there is no error, no error code and no Done.

Please help me.

Thanks