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DP83822I: RMII unused TX signals

Vladislav Shmelev
Prodigy 80 points

Part Number: DP83822I

1) Hello! Should i connect to PD unused TX_D2, TX_D3 signals (6,7) in RMII Mode or i could leave them floating?

2) Could you check connection between DP83822IRHB and OMAPL138EZWTA3? (RMII Master Signaling MODE)

Thank you very much!

DP83822IRHB + OMAPL138.pdf

  • 0
    TI__Genius 11725 points

    Hi Vladislav,

    To answer your questions:

    1. In RMII Mode, TX_D2 and TX_D3 can be left floating, they will be unused. However, if there is a need to switch between RMII and MII, in MII mode, TX_D2 and TX_D3 are required, so connections should be made. 

    2. Connections look ok. Some other schematic notes:

    • MDIO requires 2.2k pull-up
    • LED_0 1.96k pull-up is not a recommended strap mode. What is the desired strap mode for this pin? 

    Thank you,

    Nikhil

  • 0 in reply to Nikhil Menon
    Prodigy 80 points

    Hello Nikhil! Thank you for reply,

    Desired strap mode for LED_0 is Default (4), but i thought to use LED (VD20) on this pin.

    8.5.2 Datasheet Note: "LED_0 and LED_1 require parallel pullup or pulldown resistors when using the pin in conjunction with an LED and current limiting resistor. A 1.96kΩ to 2.49kΩ resistor should be used as the parallel pull resistor. When LED pins are not used, they can be left floating."

    I misunderstood?

  • 0 in reply to Vladislav Shmelev
    Prodigy 80 points

    LED_0 1.96k pull-up is ok?

  • 0 in reply to Vladislav Shmelev
    TI__Genius 11725 points

    Hello Vladislav,

    Apologies for the delay and apologies for the confusion. You are correct, a 1.96k resistor should be ok for the parallel pull resistor. Currently I see VD20 is pulled up in series with a 1k ohm resistor, without a parallel pull resistor. Please be sure to add the parallel pull.

    Thank you,

    Nikhil