byte swapping
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Maybe someone have more knowledge on this and would like to share it. I have one profibus DP slave and DP master on my network. When I configure my master and start it, I get communication (no data exchange yet). When I start data exchange the data I send is wrong. For some reason my PLC/DP master swap byte 0 and byte 1 of the word around. When I use another DP master this doesn't happen. Is it linked to the manufacturer or what? I had to write code to do the byte swapping for me. Should there be a setting in the DP master that would automatically do this?
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Hi Danie
Sorry for the late response. This is a common problem for most people. Different PLCs read in the data in different formats but most should have a function block to handle the byte swapping. It will take a bit of time to find out what type of byte swapping is needed to get the correct answer out.
Yes this is linked to the PLC manufacturer. If you google this topic you will see which PLCs swap the bytes and which dont.
There are a few different combinations for bytes swapping, so to do this automatically would be a little difficult.
Good Luck!
Brendan
PCC -
What is even more strange is that when I tested that same profibus master another slave device, no byte swapping needed...I'll do a quick test during the week just to confirm...
Why is there no standard bit structure??
Thanks for coming back to me. -
Hi Danie
Haha...I feel your frustration! Why do some cars have the indicator on the right side of the steering wheel and others not? Because they think they are right and everyone else is wrong :)
How did your test go?
Brendan
PCC
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