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Clarification on Exception from modbus master: Function Code 0x49

  • Hello,

    We're running Mango 3.6, getting sensor values for water pumps in the field. We're getting quite a few alerts back for Function code: 0x49. I know this is a CRC response generated from a value mismatch, but had a question about some other values that Mango passes along.

    What does the "Returned to normal" status really mean? Does this mean Mango received an update from the pump that the value mismatch was resolved, or is it something else?



  • Yes, returned to normal means the condition that had triggered the event is no longer true so in this case, I would assume you had some good communications in between these errors. It is normal practice to turn all your Data Source events to Ignore once the communications are working. It is not uncommon to get occasional errors like this especially if this is over a large network. You can use the Slave Monitor point to track the overall communication health. There are also data points on the Internal Data Source you can configure for tracking your Poll times and aborted polls which can be a good indication of communication health.

  • Thanks, Joel, appreciate the quick reply!