DP83849IF: Media converter : Strap/Register settings

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Replies: 9

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Part Number: DP83849IF

Hi,

I am using DP83849if chip as RJ45(PORTA) to Fiber(PORTB) media converter.

Information about my application:

Board A                                                                                                                      Board B

(RJ45+magnetic <--> DP83849if <--> FX_transceiver)       <--> FO cable  <-->        (FX_transceiver <-->DP83849if <--> magnetic+RJ45).

I use ping test to check communication between Board A & B. But I do not receive an answer.

I have attached the registers value read by µC.

1. Could you please check and let me know if the configuration settings(porta and portb) for this setup are correct?

2. Which register can give me information about the received data from FX differential signals?

3. When RJ45 is not connected, I could see the default pattern of 125MHz signal generated by Dp83849if on the FX transmit differential signals. Is that correct or something wrong ?

Thanks and Regards,

Yash

9 Replies

  • Hello Yash,

    Could you please give me more details on your application and why a dual-port PHY is being used?

    What mode are you configuring each of these PHYs to? Are you using pin-strapping and just reading back the register values or have you configured the registers as well?

    Thanks,

    Vibhu

  • In reply to Vibhu Vanjari:

    Hi,

    I need a media converter chip(Copper to optical). That's why I use dual port PHY.

    PORTA is connected to RJ45 and PORTB to optical transceiver.

    DP83849if is configured as a media converter mode with EXTENDER_EN pin enabled. I am using pin strapping and also I have configured 2 registers(PHYCR-disable auto MDIX and EDCR-disable Energy detect mode). I am reading registers values to confirm the settings.

    Please let me know if you need more information.

    Regards,

    Yash

  • In reply to Yash Naik:

    Hello Yash,

    I recommend double checking your strap settings with the datasheet and refer to section 3.4 of https://www.ti.com/lit/an/snla086b/snla086b.pdf to see if you are configuring the device correctly.

    Additionally for debugging purposes try enabling auto-neg and auto-MDIX and see if this helps isolate the issue.

    Thanks,

    Vibhu

  • In reply to Vibhu Vanjari:

    Hi,

    I checked the strap settings. All strap settings are configured correctly for media converter mode.

    Could you please tell me in detail how to use auto-neg and auto-mdix modes for debugging purpose?

    Thank you.

  • In reply to Yash Naik:

    Hello Yash,

    Thanks for confirming that the straps are correct. Sorry for my previous suggestion about auto-neg and auto-MDIX, it looks like you already have an established link.

    On further looking at your registers I noticed that the RBR register is configured to 0x04C1. Please try configuring RBR[12:9] to 1110 as suggested in Table 6-7. of the datasheet. This configures the PHY to media converter mode.In your setup RBR[12:9] is configured to 0010.

    Thanks,

    Vibhu

  • In reply to Vibhu Vanjari:

    Hi Vibhu,

    Thanks for your suggestion. As you mentioned, I tried to set the RBR[12:9]  for both ports A & B to 1110. I have read the RBR register value 0x1CC1 .

    But the communication does not work..

    I tried below setup as described in section 3.4.1 without firmware (no read & no write) to monitor the data on RXD lines for both PORTA and PORTB.

    I have noticed that the PORTA - RXD0_A to RXD3_A lines are always 0. These lines show no  pulses when I connect the RJ45 to PC. This means that the PORTB transmit pins are not transmitting.

    Can you please tell me why this is happening. Did I miss any other setting?

    Another question: Should I use Ethernet crossover cable to connect to computer if I don't use Autoneg and auto mdix feature of dp83849if?

    Thank you.

  • In reply to Yash Naik:

    Hello Yash,

    Yes, please use Ethernet crossover cable when auto-neg and auto-MDIX are disabled. Please double check to make sure that auto-MDIX is disabled when using the crossover cable.

    If this doesn't work DNP the pull-up resistor on RXD2_B/EXTENDER_EN in your schematic.

    Thanks,

    Vibhu

  • In reply to Vibhu Vanjari:

    Hello Vibhu,

    Thank you for your answer regarding crossover cable.

    If I DNP the pullup on RXD2_B/EXTENDER_EN, how does the PHY configure as media converter mode and How can I check if PORTB is transmitting or not?

    Regards,

    Yash

  • In reply to Yash Naik:

    Hello Yash,

    You can ignore that suggestion about DNP the pull-up. You can either have the pull-up or register configure that bit.

    Did the crossover cable help?

    Thanks,

    Vibhu