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DP83867E: Unit not working with 100Mbps.

ABDUL AZEEM
Prodigy 10 points
Part Number: DP83867E

Schematic for TI.pdf

Hi,

I would like to report the below problem and see if TI can help us to find rootcause. Attached the schematic.

Problem: When auto negotiate is configured ON for the DUT ethernet port and ON for the 100 Mb/s Ethernet port on the Windows PC, the DUT ethernet port configures to 1000Mb/s instead of 100Mb/s.

Performing the following will configure the DUT to 100Mb/s

  1. Forcing 100Mb/s via ethtool command:  ethtool -s eth0 speed 100 duplex full  
  2. Configuring the Windows 100 Mb/s ethernet port to auto negotiate OFF and forcing speed to 100Mb/s full duplex

Either of these configurations will allow the DUT ethernet port to operate at the correct speed.

 We have performed various tests via ethtool to confirm the DUT ethernet port to confirm auto-negotiate is enabled. A sample test is the following sequence:

  1. Reboot DUT in current failing configuration (DUT  ethernet comes up at 1000 Mb/s instead of 100 Mb/s)
  2. Using ethtool configure DUT port to 100 Mb/s with auto negotiate OFF. (DUT ethernet will configure to 100 Mb/s correctly)
  3. Turn ON auto negotiate via ethtool (This will cause the DUT ethernet to configure to 1000 Mb/s)

The unit seems to be attempting to negotiate but setting the incorrect speed (As seen in step 3). 

Regards

Abdul Azeem

  • 0
    TI__Mastermind 39845 points

    Hi Abdul,

    Thank you for the query. For schematic review, this typically takes a 5 working day turnaround. I will have an update on the schematic by 11/4 at the latest. 

    Regarding the behavior observed, are you sure the Windows PC PHY does not have the ability to operate at 1000mbps and/or has that setting disable when linking up? Whenever auto-negotiation occurs, the PHYs involved typically exchange information of capabilities (speed, MDI/MDIX, etc). In regards to speed, after exchanging information, the PHYs will agree to communicate at the highest speed common between them. When the PHY is operating after auto-negotiation occurs in 1000MBps mode, is there link at that moment?

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 10 points

    Thanks  Gerome for the reply!

    For the PC Ethernet Port we are using , It is not possible to select 1000Mb/s operating speed on PC side. and I have confirmed it is always operating at 100Mb/s via Windows Network Adapter settings. .  But there is no link at all unless we force 100Mb/s on the PHY

    Regards

    Abdul Azeem

  • 0 in reply to ABDUL AZEEM
    TI__Mastermind 39845 points

    Hi Abdul,

    Would forcing 100Mbps speed while disabling auto-negotiation on the PHY be a valid solution for you? You can disable it strapping or FW like you have done and set the speed via firmware.

    Also, may I ask how you are able to know what speed the PHY is currently at/set to via auto-negotiation

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 10 points

    Hi Gerome, 

    Were you able to do the schematic review.?

  • 0 in reply to Gerome Cacho
    Prodigy 10 points

    Hi Gerome.

    We would like to know why it is not working? 

    We can see the speed on both sides. 

  • 0 in reply to ABDUL AZEEM
    TI__Mastermind 39845 points

    Hi Abdul,

    Would disabling advertisement of 1Gbps be a viable solution? To my knowledge, most windows PC's have 1G functionality as this capability has existed for quite a while. You can disable gigabit advertisement on DP83867 by ensuring Reg 0x9[9:8] = 0x0. This will ensure that when DP83867 auto-negotiates with another PHY, at most the speed should be 100Mbps.

    In addition, here are my feedback regarding your circuit:

    - Please follow decoupling scheme located within datasheet for all power pins

    - Ensure LEDs are strapped properly. Unsure function of Q9/13

    - As Xtal is not seen, ensure component meets requirements located within datasheet

    - Within MDI subsection, there is an extra 1nF capacitor on each line of cable side center tap. Please remove to adhere to magnetic recommendation within datasheet.

    Sincerely,

    Gerome