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DP83849IF: Fiber to copper Media Conversion

Pierluigi Caputo
Prodigy 60 points
Part Number: DP83849IF

Hello,
Following the reference design (DP83849IFVS-EVK) I put the DP83849IF in one of my board with the aim of use it as a Media converter R45 to fiber.

I had some issues because the datasheet isn't really clear about the loopback of RMII signals: I think that there must be a cable between the J9 and J14 connectors.

Anyway, I tried to tie signals TX from port A to RX of port B and viceversa (port A is copper, port B is Fiber).

I read that, for RMII, it is sufficient to tie RXD[1:0] to TXD[1:0] (A to B, B to A), and RX_DV to TX_EN, with this connection pull up to VCC by a 2.2Kohm resistance.

The clock is the system clock and it's the same for the 2 ports (a 50 MHz oscillator).

The conversion doesn't happen.

Can you suggest me if there is something that I miss? Can you suggest me some way to investigate about the point where the chain interrupts itself?

Thank you

  • 0
    TI__Mastermind 23675 points
    Hi Pierluigi,

    Can you share a schematic? Do you have the pull-up on both RX_DV pins?
    Do you have a 50MHz clock source to the XI pin?

    Kind regards,
    Ross
  • 0 in reply to Ross Pimentel
    Prodigy 60 points

    Hello Ross,

    thank you for your reply.

    Your colleague Domenico Granozio should send you my schematic in private.

    Meantime, I answer your question:

    1) I put 2 pull-up on both RX_DV pins

    2) I have a 50 Mhz clock on X1 pin (oscillator FXO-HC536R-50.000)

     

    I also share with you my strap configuration (I put on my board jumper as the dev kit):

    ANEN_B                              PULL-DOWN

    AN1_B                                 PULL-DOWN

    AN0_B                                 PULL-UP

    AN0_A                                 PULL-UP

    AN1_A                                 PULL-UP

    ANEN_A                             PULL-DOWN (to force 100Mbit, no autonegotiation)

    XTENDER_EN                    PULL-UP (this should permit the internal loopback between the 2 channels MII signals)

    CLK2MAC_DIS                  FLOATING

    PWRDOWN_INT_B        FLOATING

    ED_EN_B                            FLOATING

    FX_EN_B                            PULL-UP (fiber on chan B)

    MDIX_EN_B                      PULL-UP

    LED_CFG_B                       FLOATING

    LED_CFG_A                       FLOATING

    MDIX_EN_A                      PULL-UP

    PWRDOWN_INT_A        FLOATING

    PCOL_A                               FLOATING

    Thanks

    Pierluigi

  • 0 in reply to Pierluigi Caputo
    TI__Mastermind 23675 points
    Hi Pierluigi,

    Thank you for the information. I just responded to the email thread.
    We can leave this open until the email loop is closed.

    Once we close the loop we can list the resolution here if needed.

    Kind regards,
    Ross