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AM5728: Ethernet link toggling with AM5728 based modules and Ethernet switch

Leeladhar Arja
Prodigy 150 points

Part Number: AM5728

Hi,

we are using  four AM5728 based modules along with KSZ9031 Phy for etherent.  in the backplane, a switch(KSZ9896) is being used. when try to connect all four modules to switch at 100mbps, link toggling is observed continousely. as a fall back measure, when i try to reduce the link speed with 10mpbs , link is stable. 

alternatively, i tried only two modules to switch at 100mbps and the link is stable. but if i restart any module(through init 6 command) and hold at u-boot stage, again i observed link toggling. 

requeseted to guide me with the debugging as why link is stable in normal operation and toggling when one module held at u-boot.

regards,

Leeladhar

 

  • 0
    TI__Mastermind 41526 points

    Hello,
    Thank you for your inquiry. **Josue Zamitiz** is currently on leave and will be available on **2026-09-14**.
    Your query will be addressed upon their return. We appreciate your patience and understanding.
    Best regards,
    TI E2E Support Team
    ---
    *This is an automated notification.*

  • 0 in reply to Josue Zamitiz-Ayala
    TI__Mastermind 41526 points

     ,

    Can you help me understand the setup? Please share a block diagram of the setup. 

    Best,

    Josue

  • 0
    TI__Guru 64480 points

    Leeladhar,

    4 modules at 100Mbps -> Link fail but 10Mbps-> Link ok.

    2 Modules at 100Mbps- > Link ok.

    It could indicate the signal / power integrity issue.. or s/w issue with the uboot.

    could you measure the power rails when all modules are enabled to see if the power have any voltage droop? 

    are you enabling auto negotiation; could try to do a force link to see if it works? 

    Have the TX/ RX traces phase matched and ensure no timing issues on the traces, if there is provision of the series damping resistors then you could try having 22ohm resistors on the path to reduce any ringing. 

    do you know if there are additional configs done in the normal operation like clock skew adjustment that may not be done on the uboot?