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DP83822I: Advertise only 10mbps during auto-negotiation

Abhijeet Badurkar
Prodigy 10 points
Part Number: DP83822I

Hello,

I am trying to setup the inital speed of DP83822I PHY to 10mbps. The initial speed is configured in BMCR bit 13 to 10Mbps. The ANAR register is configured in such way that PHY only advertieses 10mbps capabilities. (Register value: 0x61). The PHY is configured using Cortex-M7 microcontroller.

The PHY is communicating with an ethernet switch which has 10Mbps/100Mbps/1Gbps capabilities.

During auto-negotiation the ethernet switch advertises all of its capabilities and DP83822I only 10Mbps.The problem is that when auto-negotiation is completed the PHY is connected with 100Mbps although it did not advertiese 100Mbps.

The question is how to make sure that after auto-negotiation, 10Mbps speed is selected for communication. I do not wish to disable auto-negotiation of PHY.

Thanks & Regards,

Abhijeet

  • 0
    TI__Genius 16030 points

    Hello Abhijeet,

    Can you share the reason of not disabling the Auto-neg if 10Mbps speed is the only requirement? I am checking if the disabling advertisement is sufficient or we need to have further configuration if auto-neg is enabled.

    --

    Regards,

    Vikram

  • 0 in reply to Vikram Sharma
    TI__Genius 16030 points

    Hello Abhijeet,

    If you are disabling 100Mbps capabilities through registers after it is enabled at boot-up using strap, you will have to do a soft register after updating the register : that is you will have to write register <0x001F> = x4000 after updating ANAR register.

    --

    Regards,

    Vikram

  • 0 in reply to Vikram Sharma
    Prodigy 10 points

    Hello Vikram,

    thank you for suggestion.

    I solved the issue by setting ANAR register just after setting Reset bit in BMCR register. This set speed to 10Mbps. For all further auto-negotiations (for example, in case link is down and then up again) the speed is set to 10Mbps.

    Thanks & Regards,

    Abhijeet