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DP83848K: works at 100 Mbps, but does not work at 10 Mbps

Andrey Dolgunov
Prodigy 110 points
Part Number: DP83848K

Good afternoon.
I made a circuit based on STM32 and DP83848K. ALL according to the description. In the code in the Ethernet settings indicated auto-negotiation. I connect to the PC. In the network settings I indicate 100MBitps, there are pings. If I change the settings to 10Mbitps, there are no answers to ping. What could be the problem?

  • 0
    TI__Genius 11900 points

    Hello Andrey,

    How are you changing the settings? Do you still see an issue if you power up the PHY when the network is set to 10Mbps?

    Can you list out what your straps are configured to and any initial register settings to configure to 100Mbps? What are the changes you are making after this when you switch to 10Mbps mode?

    Thanks,

    Vibhu

  • 0 in reply to Vibhu Vanjari
    Prodigy 110 points

    Hello, Vibhu

    on STM32 I use HAL and set Init.AutoNegotiation = ETH_AUTONEGOTIATION_ENABLE in the Ethernet settings
    I change the transfer rate on the PC. after changing the settings I reboot the device according to the power - the problem persists. When I set 10Mbps, ping is absent, when I change to 100 - ping appears.

    My schem is right?

    Andrey

  • 0 in reply to Andrey Dolgunov
    TI__Genius 11900 points

    Hello Andrey,

    Please compare your schematic to: https://www.ti.com/lit/df/snlr011a/snlr011a.pdf

    On a quick look it looks like your AN1 and AN0 straps are not set to support 10BASE-T. Please refer to the strap options section. I believe you need to pull up both these pins with 2.2k resistors to advertise 10BASE-T as well as 100BASE-TX.

    Thanks,

    Vibhu

  • 0 in reply to Vibhu Vanjari
    Prodigy 110 points

    As a result, it turned out that if the settings in the firmware are the same as on the PC, then 100 Mbitps and 10 Mbitps work.

    If you specify ETH_AUTONEGOTIATION_ENABLE in the firmware,  and specify a specific speed on the PC, it only works at 100MBitps.

    About AN1 and AN0 - as I understand it, this is the initial configuration of the chip, which can be changed by the settings in the registers.

    Vibh, thanks for the help!

  • 0 in reply to Andrey Dolgunov
    TI__Genius 11900 points

    Hello Andrey,

    Glad to hear that both speeds work now. I will close this ticket now.

    Your understanding is correct regardless of the straps you can use register configuration after the initial strap configurations.

    Thanks,

    Vibhu