DP83848C: tx error in host computer in SNI Mode

Prodigy 30 points

Replies: 4

Views: 101

Part Number: DP83848C

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 ?

4 Replies

  • 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

  • In reply to Vibhu Vanjari:

    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.

  • In reply to Gyu Youn Song1:

    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

  • In reply to Vibhu Vanjari:

    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.