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TM4C129ENCZAD: How to disable ethernet functionality from the board

Lesser Horned Owl
Prodigy 140 points
Part Number: TM4C129ENCZAD

Hello,

I want to have the option to disable the ethernet MAC and PHY of the TM4C129ENCZAD at the board level. I would like to know whether it is sufficient to leave the following dedicated pins unconnected:

  • EN0TXOP/N
  • EN0RXIP/N
  • RBIAS

or whether additional circuitry is required.

Internally, from section 23.3.1.1 of the datasheet, I see that the SYCLK to the MAC can be gated off. I will plan to do that as well. I don't see a method for disabling the PHY.

I do also see that the power-down mode may be enabled as specified in 23.3.10. Please advise on how to properly disable ethernet.

Thank you.

  • +1
    TI__Guru*** 135355 points

    Hello,

    On any device with an Ethernet PHY, you have to beware of Errata ETH#03 which states that the RBIAS resistor is required to be populated regardless on if you are using the Ethernet peripheral.

    Regarding the other elements, you can leave the remaining Ethernet pins unconnected. There is no need for software adjustments as the Ethernet MAC and PHY would not be enabled by default. The clock gating wouldn't be required either because the clock gating isn't enabled until you use an API like SysCtlPeripheralEnable(SYSCTL_PERIPH_EMAC0).

    Best Regards,

    Ralph Jacobi

  • 0 in reply to Ralph Jacobi
    Prodigy 140 points

    Perfect answer, thank you!