TIA portal - modbus RTU intermitent fault

rQx said:

Yes, that is what I do. Wait for DONE or ERROR signal and then move on. I wonder if I should have more time after this so be 100% sure the previous block is inactive.

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At least 151-8 CPU didn't like if time between Modbus serial querys was zero or too fast.
It halted CPU to stop on testing



p.s I had writing error on answer, it should have write if Done or error bit isn't setted.

Maybe I cold add an inverted BUSY bool in series with the REQ on my blocks. This would make the new block only take a REQ signal if the previous isnt busy and also just make a REQ that is active untill the block is activated. Or is it better with timer that I can add a longer tine?

Photos of wiring?
Or detailed description?
What cable or wire did you use, ideally datasheet.
Sounds like noise.

It's internal wiring so I have used only non isulated multicore cables that I have twisted. I have used this in the past with no problem, but maybe I have more interferance now and should use a shielded cable? The distanse between PLC and drives is like 30cm

I have monitored the bus voltage of one of my drives and I have recorded 14 dips below 100V (usually 570V)in the past 12 hours. The only thing that can dip this voltage is a shutdown of the VFD and that has not happened. I assume that I get corrupted data back from the VFD or that the MB_Master block is zeroing my data pointer when I get an error? I haven't recorded number of errors of the block so can't say for sure that the actual block has gotten error 14 times