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ISO1176: rs485 AB PIN swap influence

Gene Qiu
Intellectual 1720 points
Part Number: ISO1176

Hi Team

When using ISO1176, if A B pin connected with DP interface wrong inversely, what kind of the influence would have?

currently it is inversely connected, but communicate normally.  While correct the connection, failed to communication. 

Best Regards

Gene

  • 0
    TI__Mastermind 47895 points

    Hi Gene,

    The A and B pins on RS-485 transceivers (including the integrated one in ISO1176) are identical and electrically won't care about being inversely connected. However, to the system, all information transmitted or received by this node will be inverted. This is commonly corrected in software or by use of transceivers with polarity correction features (not included in ISO1176). 

    I would recommend checking the bitstream of the failed communication when the system is connected in the correct orientation to verify that the data is not inverted. If the software is unable to do this, an oscilloscope connected to the A/B pins or R pin of any active transceiver on the bus can be used. '

    *Note that RS-485 transceivers will not be electrically harmed by inverted connections, but other parts of the system such as biasing networks or other driving transceivers may interrupt or damage incorrectly connected devices.

    Let me know what you are able to find out in the failing test case. Please share any other questions you may have.

    Regards,
    Eric