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Original question:

Back to back Gigabit Ethernet Phys???

DP83867CR: Back to Back PHYs work as a repeater, but can they also mirror the ports?

Keith Mecham
Prodigy 70 points
Part Number: DP83867CR

TI's AN-1509 detailed several configurations of PHYterDual port switching, including one where port A and B acted as a repeater, but the RX data from each port was also mirrored to the MAC over MII/RMII.  This is a very useful feature, and even though TI's Gigabit Ethernet PHYs don't come in a dual package, I was hopeful I could pull it off.  Rod Rodrigues responses in the thread below about using the DP83867 back to back made me wonder if I could accomplish the desired repeater with port mirroring function for Gigabit Ethernet.

(+) Back to back Gigabit Ethernet Phys??? - Interface forum - Interface - TI E2E support forums

Would it work to tie in an RGMII MAC to the RX lines for each port? to accomplish this?  (see image from AN-1509 pg 8 below)

  • 0
    TI__Mastermind 26320 points

    Hi,

    Back-2-back mode is possible with RGMII. Port Mirroring normally involves snipping the lines and replicating the data. Can you share block diagram of the application you are trying to achieve.

    Regards,

    Geet

  • 0
    Prodigy 70 points

    Hi, and thanks for helping with my question.  I want to take a 1Gb Ethernet connection between two devices and re-direct them into my 'port monitor'.  I hope that the PHYs can repeat the data received from the connected device so they appear to be connected together by an Ethernet repeater - not a switch.  Then I hope to feed the RX data from each PHY into an FPGA for analysis.  The FPGA can provide the MAC functionality.  I planned to use RGMII for the interfaces.  I believe this should work unless the PHY cannot handle driving the TX input on both the other PHY and the MAC. 

  • 0 in reply to Keith Mecham
    TI__Mastermind 26320 points

    Hello,

    Thanks for sharing the block diagram.

    RGMII interface is high speed DDR interface with max capacitance of 5 pF drive. You have to ensure you are not loading the lines beyond the limits else may run into timing violation issues.

    Regards,

    Geet