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SN65MLVD206: RE/DE Shorted together

Alexandre Bernussi
Intellectual 1955 points
Part Number: SN65MLVD206

Team,

I have a question from a customer per the below circuit configuration. Is it OK to short the two signals - RE+DE and R+D?

The two signals RE+DE and R+D are wire-ored. The R/D signal is being used for SPI clock connected to a controller. The controller can be master or slave hence the need to drive or receive the clock signal. 

I appreciate the help!

  • 0
    TI__Mastermind 35130 points

    Hi Alexandre,

    It's fine to have RE+DE shorted. It is not recommended to short R+D however, as the stub created by this as well as additional loading from the driver/receiver may result in signal integrity issues.

    Regards,

    I.K. 

  • 0 in reply to Ikechukwu Anyiam
    TI__Intellectual 1955 points

    Thank you for the quick response I.K. Is there a way to help to minimize this stub impact? From the customer, the R + D pins are tied directly to the pins and the connection to a microcontroller is only 14mm away. If this remains the recommendation, is there a different path to take given the desire for the controller to be capable of being both a master and a slave. 

    -Alex

  • 0 in reply to Alexandre Bernussi
    TI__Mastermind 35130 points

    There's not much you can do to minimize stub impact other than eliminate the stub altogether. I will say I've seen other customers tie R+D pins together and not see any issues, but it is still not recommended as the part was designed with the half-duplex feature on the A and B pins, not the R and D pins.

    Regards,

    I.K.