Dear Masters,

Recently I am facing problem for Modbus master application on s7-1200 plc with cm1241 module,

before the new firmware updated for s7-1200 cpu, everything was fine, but then after it updated, seem sometime my modus master block is doing nothing with no feedback Boolean status bit like DONE or ERROR. Thus, the ladder sequence will just hang there.

remarks: this happen sometimes only if the slave is down, the only solution now is restart or re-run the plc.....but after awhile, it will back to this problem again.

anyone experienced this issue? how to solve...thanks.

I am facing similar problem with you.

PC communicate with PLC via modbus-TCP. I have been using it two years more than 20 system with no problem.

 After I updated TIA Portal V13 SP1 UP2, communication between PC-PLC disconnected.

to connect them again I must restart the PLC.

I cant find any solution.

Maybe this will help. 

CM 1241 V2.1:

https://support.industry.siemens.com/cs/document/108819199/firmware-update-v210-for-cm-1241?pnid=13683&lc=en-WW

CPU V4.1:

https://support.industry.siemens.com/cs/document/106200276/firmware-version-v41-released-for-s7-1200-cpus?pnid=13683&lc=en-WW