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DP83867IS: DP83867IS how can i switch between 100/1000

Stephan Koprivsek
Prodigy 40 points

Part Number: DP83867IS

Hi everybody,

i am having issues by switching between 100 Mbps and 1000 Mbps modes. When auto-negotiation is enabled, the PHY is able to switch between 100 and 1000 but only if the PC side is limited to the specific data rate.

But i want to configure the PHY manually, so the PC builds up a 100 Mbps link when i configure the PHY in 100 Mbps mode. For that i turned in register 0x0000 bit 12 to "0" to disable auto-negotiation. Bits 6 (MSB) and 13 (LSB) turned to [01] for 100 Mbps and bit 8 to "1" for full duplex.

The RGMII side is running on 25 MHz but the ethernet side cant build up a link.

Many thanks for your help.

  • 0
    TI__Mastermind 18425 points

    Hi Stephan,

    When you disable autonegotiation are you also disabling Auto-MDIX (register 0x10)?

    Another option is to disable 1000Mbps advertisement but keep auto-negotiation enabled. This will prevent link from resolving to 1000Mbps and will come down to 100Mbps. For this, leave register 0x00, 0x04, and 0x10 in their default configuration and then write 0x0000 to register 0x09. 

    -Regards

    Aniruddha

  • 0 in reply to Aniruddha Khadye
    Prodigy 40 points

    Hey Aniruddha,

    sorry for the late response!

    I disabled 1000Mbps as you said. 100Mbps is working when the cable is reconnected so a new link is build up. By setting bit 9 of register 0x0000 a new auto-negotiation process is started.

    With this the cable can stay plugged in and the data rate changes between 100Mbps and 1000Mbps. Many thanks to you!

    Kind regards

    Stephan