AM5729: KSZ9031RNX IC - link is up without connecting cable

Hello Peta,

This might be an issue with your set-up of the PHY and does not pertain to the AM57x device. See some of these existing threads:

• https://e2e.ti.com/support/processors-group/processors/f/processors-forum/488872/am335x-gigabit-ethernet-ksz9031-auto-negotiation/2257360#2257360
• https://e2e.ti.com/support/interface-group/interface/f/interface-forum/627425/problem-with-connection-between-two-phy-ksz9031rnx

This issue is more than likely a hardware setup issue.

-Josue

Hi Josue,

We verified Power section and Clock section of Setup completely and it correct, we have verified the hardware section everything looks fine, if you are suspecting anything please let us know we will verify that also.

Hello, 

I am out of office until the 21st of the month. 

I appreciate your patience.

-Josue 

Hello Peta,

Can you please confirm that the recommendations were followed from the AM57x Schematic Checklist on this design? As well as the recommendations from High-Speed Interface Layout Guidelines (Rev. J)?

PETA MAHESWAR REDDY said:

Thanks in advance.

Not sure if this was supposed to be  a schematic, could you please share your schematics for this connection?

-Josue

Yes, we followed the Schematic check list and layout guidelines of AM5728 design.

Around 10 boards, we are facing this issue only with one board. Is there any processor issue or phy IC issue. Even we replaced PHY chip and RJ45 port. Is there any way to confirm from issue with processor. Please provide your suggest.

Peta,

Very interesting that you see the link up without having a cable.

I wonder if it could be due to any reflections on the TX / RX lines on the board when its not connected to anything. Was any termination done when this was tested, or could you try one?

Have you also tried following the suggestions on the e2e that Josue linked about adding filter caps to the power supplies to see if this mitigates the issue?