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Original question:

LP-AM261: Phy on fixed speed need seconds to establish a link

DP83826E: DP83826E phy takes 2-3 sec in worst case for link up

Nilabh Anand
Mastermind 45824 points
Part Number: DP83826E

Tool/software:

Based on the customer observation in the realated thread the dp83826E phy takes 2-3 sec in worst case for link up. This observation is seen with forced negotiation i.e 10/100M full duplex/half duplex.

Would you please help to understand the reason for this behaviour.

  • 0
    TI__Genius 14116 points

    Hi, 

    Does this behavior happen when auto-negotiation is turned on and only certain speed/duplexes are advertised?

    Best,
    J

  • 0 in reply to J
    TI__Mastermind 45824 points

    It happens with both the cases. Initial thought was it could be because of autoneg. So we tried to test forced then also we have observed same behaviour.

  • 0 in reply to Nilabh Anand
    TI__Genius 14116 points

    What is the cable length that this is happening? Does this behavior seen only on one PHY, or multiple boards? Does this happen with all link partners?

    Please let me know. 

    Best,

    J

  • 0 in reply to J
    TI__Intellectual 1710 points

    Hi,
    for clarifying the context in which the problem shows up: 
    If the PHY is configured for fixed speed (10/100) and the link partner is also is configured accordingly, the link can establish 50% of the time immediately, but if the Ethernet cable is unplugged and plugged back, sometimes it takes several seconds until the link is established.
    Cable length were short (1m Maximum) in tests performed.

    In Auto-negotiation mode, the link can be established fast enough, the problem has been observed in Fixed mode only.

    Best regards,
    Pourya

  • 0 in reply to Pourya Eskandari
    TI__Genius 14116 points

    Hi Pourya, 

    Thank you for your detailed response. 

    Using auto-negotiation is more robust with TI PHYs than forcing speed. We recommend enabling auto-negotiation and disabling the certain modes you don't want to link up for faster reaction time instead of forcing the speed/duplex. Please let me know if only advertising certain speed on auto-negotiation still takes few seconds to connect. 

    Best,
    J

  • 0 in reply to J
    TI__Intellectual 1710 points

    Hi,

    for the Protocol (EtherNet/IP) which they are using the PHY for, it is one the requirements that the PHY should also work with Fixed mode robustly. Auto-negotiation alone is not enough.  
    Based on your answer, it means, is it a known issue with this PHY?
    Is there any other PHY you could recommend, or is there something they could do via configurating the PHY registers?

    Best regards,
    Pourya

  • 0 in reply to Pourya Eskandari
    TI__Genius 14116 points

    Hi Pourya, 

    Because the IEEE 802.3 standards do not specify requirements for testing multivendor interoperability with autonegotiation disabled, enabling autonegotiation on guarantees the PHY to be more robust with other link partners. 

    Best,
    J