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DP83TC813S-Q1: Testing DP83TC813x-Q1 with external loopback

Benjamin Horton
Prodigy 10 points

Part Number: DP83TC813S-Q1

Hi, I am making a test board for a board that uses this phy, and I want to be able to test external loopback, i.e. generate packets out of a port, and loop it back and verify its the same. This phy seems to mainly discuss internal loopback, but I want to use external loopback in order to test the physical link to the connector fully. The datasheet seems to hint toward external loopback in a couple places:
image.png
Here, it refers to "cable side" generation and checking.
Also here it talks about external loopback mode in the registers:
image.png

I am wondering if I can use this "cable side" packet generator and checker, and on the hardware side, route the P and N cables for an ethernet port to the tester, and terminate with 100 ohms so that the data is effectively routed right back to the same port:
image.png

  • 0
    TI__Expert 6052 points

    Hi,

    Benjamin Horton said:
    terminate with 100 ohms so that the data is effectively routed right back to the same port

    100Base-T1 is a full-duplex communication standard over a single twisted pair cable. To loop back TX packets to the RX on the MDI side, another PHY which participates in 100Base-T1 link-up and communication is needed. 

    On the tester board, you can use another DP83TC813 PHY in reverse loopback mode: 

    Best,

    Charles