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DP83848C: tx error in host computer in SNI Mode

Gyu Youn Song1
Prodigy 30 points
Part Number: DP83848C
Other Parts Discussed in Thread: DP83848I

Hello,

I have designed the custom Ethernet board as like:

1) host computer : MPC860 / NXP

2) Ethernet PHY : DP83848C

   - MAC Interface Mode : 10Mb SNI Mode

In Link-off condition, ping from MPC860 to other PC is OK,

but  after Link-off and Link-on again,then  MPC860 does not send TX signal normally.

To analysis the fault condition, I measured TX_CLK signal  in DP83848C.

In normal condition, link-up, TX_CLK is 10MHz.

After that when link is changed into Link-off, TX_CLK is changed to 25MHz.

So TX_CLK, 25MHz, is asserted into MPC 860 that is set  into speed 10Mbps.

Is it correct operation in SNI Mode of DP83848C ?

  • 0
    TI__Genius 11900 points

    Hello,

    What happens when the link is established again after the reset? Does the TX_CLK go back to 10 MHz.

    "After that when link is changed into Link-off, TX_CLK is changed to 25MHz." How is this happening, could you elaborate?

    Thanks,

    Vibhu

  • 0 in reply to Vibhu Vanjari
    Prodigy 30 points

    Board configuration is like:

    MPC860 -- DP83848I -- Transformer -- Ethernet Connector - PC

    DP83848I is set to 10Mb SNI Mode  (MII_MODE = 1, SNI_MODE = 1)

    The value of TX_CLK output is changed by DP83848I Link State itself.

    When DP83848I is Link-On state (Ethernet Connector is connected with PC), TX_CLK output is 10MHz.

    If DP83848I is Link-Off state (Ethernet Connector is disconnected with PC), TX_CLK output is 25MHz always.

    Your question: What happens when the link is established again after the reset? Does the TX_CLK go back to 10 MHz.

    Yes, TX_CLK goes back to 10MHz because of Link state of DP83848I is On.

    Thanks.

  • 0 in reply to Gyu Youn Song1
    TI__Genius 11900 points

    Hello,

    Thanks for answering my question. Can you please check the register status when connector is disconnected to see if the PHY is still in SNI mode?

    -Vibhu

  • 0 in reply to Vibhu Vanjari
    Prodigy 30 points

    In custom board, 3 Ethernet ports are needed.

    So DP83848I MDC/MDIO is not connected into CPU MPC860 because of lack of available pin in MPC860.

    Thanks.

  • 0 in reply to Gyu Youn Song1
    TI__Genius 11900 points

    Hello,

    Please provide me the following information. It will be difficult to continue the debug without the MDIO interface.

    1) How are you determining that the link is off?

    2) Can you configure to the MII interface to check and see if it works? This will help further narrow down the issue.

    3) Is the issue seen on all 3 Ethernet ports?

    Please provide any other information regarding the configuration that you think is important.

    Thanks,

    Vibhu

  • 0 in reply to Vibhu Vanjari
    TI__Genius 11900 points

    Hello,

    I am closing this thread, please reopen a new one, when there is new information.

    Thanks,

    Vibhu