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SN65HVD75: Question of RS-485 mode

Lee, Sam
Expert 6065 points
Part Number: SN65HVD75
Other Parts Discussed in Thread: SN65HVD71

Hi team,

Can you give a simple answer for customer's questions?

-. For RS-485 communication, is it possible to set both DE and /RE to active (DE with pull-up, /RE with pull-down) simultaneously?

-. Is there any RS-485 device without DE, /RE pin?

Thanks,

Best Regards,

Sam Lee

  • 0
    TI__Intellectual 840 points

    Hi Sam,


    Yes you can pull-up DE and pull-down RE simultaneously. This would be a good way for your Micro controller the listen to what it is sending out, to make sure the data being transmitted is correct. 

    As for the device without any DE/RE pins, We do not have any half-duplex devices without DE/RE pins. We do have full-duplex devices without DE/RE pins such as SN65HVD71.

    This set-up would not allow for this node to receive any data from other nodes and would inhibit other nodes communicating to one another because if DE is high and D is open line A would be high and line B would be low by default, there by overriding the bus in a half-duplex set-up. One of the more normal applications is to pull-down, or tie to ground, the RE pin, and control the DE pin with an MCU so you can turn off the driver and listen for one of the other nodes to respond. 



    Regards,
    Daniel Noel