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DP83869HM: Strap pin

Moshe Tweena10
Prodigy 30 points

Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869

Hi,

I am using the Ethernet PHY DP83869HM in my new design.

I configure the PHY to Media Converter mode (1000Base-T to 1000Base-X) by strap pins OPMODE[2,1,0]=100 according to Table 7-12 "Functional Mode Strap Table" in PHY data sheet.

It works fine but I have some LINK issues when remote Host (connected to this PHY by RJ45) is being powered-up of rebooted.

At Table 7-19 "1000M Media Strap Table" I see that pin LED_0 is used as starp pin for "Fiber Auto Negotiation" or "Fiber Force Mode".

Since the PHY is configured to "1000Base-T to 1000Base-X" it means that always one side of the PHY is connected to copper and one side to fiber optics.

Can you please explain the meaning of this strap pin and when is correct to use  "Fiber Auto Negotiation" or "Fiber Force Mode".

Best Regards,

Moshe

 

 

 

  • 0
    TI__Mastermind 36085 points

    Hi Moshe,

    Fiber autonegotiation in this context refers to whether the PHY performs autonegotiation on the fiber lines by advertising 1000Mbps and going through the negotiation process before sending data. In fiber force mode, the PHY will skip the auto-negotiation process and begin sending data once a link has been established. Whether this strap is set or not, the DP83869 will only link up at the set speed (in this case 1000Mbps). Leaving this on is ok to do incase the attached link partner expects autonegotiation.

    What sort of link issues are you seeing? Does the link drop when remote host is powered up?

    Best,

    Shane

  • 0
    Prodigy 30 points

    Hi Shane,

    Yes, the problem I see is that link dropped when remote host is being powered up of rebooted.

    I have succeeded to overcome this problem only if LED_0 strap is set to "Fiber Force Mode".

    I think I will just leave it like this.

    Best Regards,

    Moshe

  • 0 in reply to Moshe Tweena10
    TI__Mastermind 36085 points

    Thank you for the update Moshe,

    Best,

    Shane