This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DP83869HM: DP83869HM in 1000M Media Convertor Mode not working

Part Number: DP83869HM

I have the same problem  with DP83869HM in 1000M Media Convertor Mode as in e2e.ti.com/.../3144830. Is there a solution to that problem?

  • Hi Alexander,

    You may want to add a digital restart to the register programming sequence such that it reads the following:

    • Write 0x0044 to register 0x01DF
    • Write 0x1140 to register 0x0000
    • Write 0x5048 to register 0x0010
    • Write 0x1140 to register 0x0C00
    • Write 0x1FFC to register 0x01EC
    • Write 0x4000 to register 0x1F

    Are you able to correctly access the extended registers? Can you read back the STRAP_STS register?

    Thank you,

    Nikhil

  • Hello Nikhil,

    I programmed the following registers:

    • Write 0x0044 to register 0x01DF
    • Write 0x1140 to register 0x0000 
    • Write 0x5048 to register 0x0010
    • Write 0x140 to register 0x0C00  (because the fiber on other side support only forced mode 1000M)
    • Write 0x1FFC to register 0x01EC
    • Write 0x4000 to register 0x1F

    After programming  links on my PC and Fiber side goes down.

    Here are the values that I have read out of some of the registers.

    BMSR = 0x7969  (bit  LINK_STS1 =0)
    STRAP_STS  = 0x08CE
    FX_STS = 0x6149 (bit  STTS_LINK_STATUS=0)
    1KSCR = 0xF000
    SERDES_SYNC_STS = 0x0220

    I don't understand why bits *LINK_STATUS in DP83869HM show the Link Down, but on PC and FIber side show the Link Status is Up?

  • Where can I get a 0x01EC register description? There's no description of it in the DP83869HM datasheet .

  • Hi Alexander,

    Can you share a schematic with us? 

    Thank you,

    Nikhil

  • Hello Nikhil,

    here is a part of my schematic in attach file

    SCH_GbE_Phy.pdf

    Thank you

  • Hi Alexander,

    I have the following feedback for the schematic:

    • SGMII pins: Use 0.1 uF caps
    • MDC: Remove pull-up
    • MDIO: use 1.5k pull-up
    • INT/PWDN: recommended 2.2k pull-up
    • Check the clock and capacitors C278, C279 meet specs described in section 10.2 of the datasheet.

    As an additional debug step, have you tried the Media Converter mode using two DP83869s?

    Thank you,

    Nikhil

  • Hello Nikhil,

    I have replaced:

    • SGMII caps to 0.1 uF
    • Checked and changed XTAL and caps C278, C279 to other
    • MDC, MDIO and INT pull-up resistor unrelated to this issue. MDIO interface works fine.

    The situation has not changed.

    I can't check two DP83869s in media converter mode on my board.

    What does the register 0x01EC do? There's no description of it in the DP83869HM datasheet .

    I tried to change the operating mode to SGMII to Copper in DP8369. Then i read register BMSR = 0x796d  (bit  LINK_STS1 =1).

    When changing  the operating mode to 1000Base-T to 1000Base-X in DP8369.  register BMSR = 0x7969  (bit  LINK_STS1 =0).

    What is the difference in these modes for the 1000BASE-T communication procedure? Why is it in the media converter mode  link  bit is down?

    Thank you

  • Hi Alexander,

    Are you also seeing this issue in RGMII to Fiber mode? If RGMII to Fiber works, this may narrow down our issue to the Fiber side. .

    Register 1EC is a link loss pass through register. If you have the PHY acting as a media converter between a Fiber and Copper device, both devices will show link on either side of the PHY. If one device, for example on the fiber side of the PHY, drops link, you would also want the device on the copper side of the PHY to drop link so this device isn't sending messages to the PHY while there is no link on the Fiber side. Enabling link loss pass through will recognize that link has dropped on one side of the PHY, and drop link on the other side. 

    Thank you,

    Nikhil

  • Hello Nikhil,

    The problem has been solved. After examining the behavior of DP8396, the following was found:
    If the 1000Base-T to Fiber mode is set using strap resistors. When the power is on, the contents of the registers are as follows:

    •  bit LINK_STS1=0 in BSMR register
    • - bit SYNC_STATUS=0 in SERDES_SYNC_STS register
    • - bit STTS_LINK_STATUS=0 in FX_STS register

    and so there was no connection.


    Then I set the SGMII to Copper mode using strap resistors. When I turned on the power, the contents of the registers were like this:

    • bit LINK_STS1=1 in BSMR register
    • bit SYNC_STATUS=1 in the register SERDES_SYNC_STS
    • bit STTS_LINK_STATUS=0 in FX_STS register

    there was no connection.
    After that, I programmed the following via MDIO:

    • write 0x0044 to register 0x01DF
    • write 0x4000 to register 0x1F

    and then the connection appeared and worked well and the register contents were like this:

    • bit LINK_STS1=1 in BSMR register
    • bit SYNC_STATUS=1 in the register SERDES_SYNC_STS
    • bit STTS_LINK_STATUS=1 in FX_STS register

    Although the problem is solved, I am interested in whether the 1000Base-T to Fiber mode should work if the setting is made only with strap resistors and there is no possibility to adjust it by software?

    Thank you

  • Hi Alexander

    For the case where you are strapping SGMII to Copper, you are reading bit LINK_STS1=1 in BSMR but there is no connection?

    As for using Media Converter mode with only straps, the datasheet specifies in section 9.4.7 that a register write is necessary for operation in Media Converter mode. 

    Thank you,

    Nikhil