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DS125BR401: DS125BR401 : 10G Link random error issue

Esakki Durai
Prodigy 120 points
Part Number: DS125BR401
Other Parts Discussed in Thread: DS100KR401

Tool/software:

Hi Team,
            We are using DS125BR401SQE/NOPB in our design for 10G Ethernet links (Do not require link training ) from FPGA to SFP+ interface through back plane connections. We set the redriver in limiting mode by connecting mode pin with pull down resistor to GND.

During 10G Link validation test we observed that out link is getting up, But it creating errors randomly. We tried to optimize the link setting (VOD,EQ,DEM) of DS125BR401S, but still we can not achieve the error free channels.

We configured SD_TH in high state and we set the below mentioned signal detect registers for forcing forcing the Signal Detect function to be always ON.
0x0D[1]= 1'b, 0x14[1] = 1'b, 0x1B[1] = 1'b, 0x22[1] = 1'b
 0x2A[1]= 1'b, 0x31[1] = 1'b, 0x38[1] = 1'b, 0x3F[1] = 1'b

Observation 1:

We can able to achieve the error free channel while we set redriver during INB to OUTA loop back  mode by writing 21 value in 0x02 register.

We attached the current redriver register value for your reference. Refer attached image for loop back scheme diagram.

After validating back plane level loop back testing, we set 31 value in 0x02 register for normal operation in that case our link itself not active. So we programmed 50 value in 0x08 register & 20 value in register (0E,15,1C,23,2B,32,39 & 40) for idle control from registers to set output ON function.
In this case 10G link up but still we have random error.

Question 1: Can you please suggest what is the suggested setting for 10GbE interface in optical link(With out Auto Negotiation)?

Question 2: In 9.5.1.1.1 section of DS125BR401 data sheet mentioned that “This data loss can be eliminated by disabling automatic detection and forcing the Signal Detect function to be always ON”

How to disable the automatic detection in  DS125BR401?
What are register I need to overwrite for this operation?


Thanks in advance,
Esakki.

  • 0
    Prodigy 120 points

    Redriver Register values.txt
    Fullscreen
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    Sl.No Register Values
    1 0x02 21
    2 0x06 18
    3 0x2D A9
    4 0x34 A8
    5 0x3B AB
    6 0x42 A9
    7 0x10 A8
    8 0x17 A8
    9 0x1E A8
    10 0x25 A8
    11 0x2E 0
    12 0x35 0
    13 0x3C 0
    14 0x43 0
    15 0x11 0
    16 0x18 0
    17 0x1F 0
    18 0x26 0
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

  • 0 in reply to Esakki Durai
    TI__Mastermind 23905 points

    Hi Esakki,

    Which RX-detect setting are you currently using? For 10 GbE applications, manual RX-detect with input termination of 50 ohm should be used. This can be configured by pulling the RXDET pin high or programming 0x08[3]=1, 0x0E[3:2]=11, 0x15[3:2]=11, 0x1C[3:2]=11, 0x23[3:2]=11, 0x2B[3:2]=11, 0x32[3:2]=11, 0x39[3:2]=11, 0x40[3:2]=11.

    "Disabling automatic detection" refers to using manual RX-detect setting.

    Have you tried using loopback IN_A to OUT_B? I'm curious if this configuration resulted in no errors as well.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Prodigy 120 points

    Hi Lucas,
        We are using manual RX-detect with input termination of 50 ohm    option only. We already pulled RXDET pin high  through pull up resistor to VDD. So currently we set redriver in manual Rx- Detect settings only.
    We tried loop back in IN_A to OUT_B path, We can able to achieve the error free channel.

    We are facing issues while we set 0x31 data in 0x02 Address for normal operation.

    Question 1: Can you please suggest is there any other settings for 10GbE interface we need to program?

    Thanks in advance,
    Esakki.

  • 0 in reply to Esakki Durai
    TI__Mastermind 23905 points

    Hi Esakki,

    Thank you for your feedback. I'd like to check, what testing was performed to optimize EQ, DEM, and VOD values? Optimizing these values is critical to error free operation. My recommendation is to optimize these values based on eye opening.

    1. Connect a high-speed sampling oscilloscope at the SFP port. Transmit PRBS data from the FPGA. Focus on one channel at a time, starting with EQ optimization.
    2. Start with minimum EQ setting and measure eye width/eye height on the oscilloscope. Step up the EQ, one index at a time, monitoring the eye width/eye height. Choose the optimal EQ setting based on maximum eye opening.
    3. Step through VOD and DEM values to optimize eye opening while maintaining the necessary peak-to-peak amplitude.
    4. Repeat steps 2-3 on the other 3 B channels.
    5. Is your FPGA able to measure diagnostics like eye width and eye height? Transmit PRBS data from the SFP port. Focus on one channel at a time, starting with EQ optimization.
    6. Repeat steps 2-3, focusing on each A channel one at a time.

    Additionally, is this E2E thread related? If this is the same project, can you clarify if DS125BR401 or DS100KR401 is being used?

    https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1416885/ds100kr401-10gb-ethernet-link-random-error

    Best,

    Lucas