MaxJustus90 Posted March 1, 2021 Report Share Posted March 1, 2021 Hi, I hope you might help with the following issue: I wrote a simple python library, using the PCOM protcol & pySerial. To test it, I created a script that reads a few Memory Bit operands from a SM-43 via the built-in RS232-USB Bridge. The library and the script work perfectly, accept when it comes to reading more than seven bit operands: I used the online mode to set the MB100-107 to the values : 10101100. While the response comes back intact, ( checksum checks out etc) I'm getting different responses for the same request. The respective bytes in the payload of the response message vary between: 0x3521 0x3523 0x3544 0x3543 0x35cb Note that I made sure that the actual bit values in MB100-107 do not change The response is consistent, as long as I don't change the status of MB107. However, as soon as I'm toggling MB107 on and off again, i get a different response from the PLC afterwards. I also get a different response when I change the read request and then go back to the old read request. The first seven bits do not seem to be affected by this - They show 0x35 consistently. Maybe I overlooked something? Thanks in advance for any hint! Max Quote Link to comment Share on other sites More sharing options...
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