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DP83867CR: Register for Ethernet Compliance Test

Akihiro Yamamoto
Prodigy 40 points
Part Number: DP83867CR

Tool/software:

Hi,

I have a question about the Ethernet compliance test for DP83867CR.

In the Application Note "How to Configure DP8386x for Ethernet Compliance Testing," the following information is provided:
Reg 0x1D5 = 0xF508 //Increases VoD swing. This register can be applied in other test scripts as well as in end-use case applications.

I would like to know the function of this register. It seems to increase the output swing, is that correct?

When I conducted the compliance test on a board with my DP83867CR, all the 1000base items passed when the register was enabled. However, when the register was disabled, the following two items failed:

1000 Base-T, Point A Peak Output Voltage (w/o Disturbing Signal)
1000 Base-T, Point B Peak Output Voltage (w/o Disturbing Signal)

It was mentioned that the register can be enabled for use in the product. Since the test results show a pass when enabled and a fail when disabled, it seems better to enable it in the product. Is this understanding correct?

If it is not enabled, what possible effects can be expected? For example, could lower voltage lead to increased data transmission errors?

Thanks

  • 0
    TI__Genius 14116 points

    Hi Yamamoto-san, 

    Akihiro Yamamoto said:
    I would like to know the function of this register. It seems to increase the output swing, is that correct?

    Yes, it is correct. 

    Akihiro Yamamoto said:
    It was mentioned that the register can be enabled for use in the product. Since the test results show a pass when enabled and a fail when disabled, it seems better to enable it in the product. Is this understanding correct?
    Akihiro Yamamoto said:
    If it is not enabled, what possible effects can be expected? For example, could lower voltage lead to increased data transmission errors?

    Not necessarily. Compliance test is designed to see the system's performance in the worst case scenario, and the standards to pass the test are very strict to ensure that the system is able to transmit with minimal issues. The performance could be better by enabling this feature. However, increasing VOD can have other consequences like increased power consumption. Enabling this feature will depend on the customer's priority on the system. 

    Please let me know if you have any additional questions. 

    Best,

    J



  • 0 in reply to J
    Prodigy 40 points

    Hi J-san,

    Thank you for your reply.

    >Enabling this feature will depend on the customer's priority on the system.

    I understand that I can choose whether to enable it if I want to prioritize quality, or disable it if I want to prioritize power consumption, etc.

    Please let me know for reference.
    What is the design intent of the DP83867CR?
    Which of the following 1-3 applies?

    1. The compliance test can be passed with the register disabled, and the product is used.
    2. Compliance can be passed with the register enabled, and the product is used with the register disabled.
    3. The compliance test can be passed with the register enabled, and the product is used.

    The register setting guide during testing had it enabled, so I would like to know if the design assumes that compliance cannot be passed with the register disabled.


    Thank you
    Akihiro

  • +1 in reply to Akihiro Yamamoto
    TI__Genius 14116 points

    Hi Yamamoto-san,

    Both 2 and 3 are true. We have seen that there is much better margin when the register is enabled from the customer. Some customers preferred to keep higher voltage swing for better signal quality over long cable length.

    Best,

    J

  • 0 in reply to J
    Prodigy 40 points

    Hi,J-san

    Thank you for your reply.
    your response was very helpful.

    I understand them.

    Thank you.
    Akihiro