• State
  • Replies 8 replies
  • Subscribers 35 subscribers
  • Views 120 views
  • Users 0 members are here
Support feedback
Options
Options
Related

Original question:

DP83822IF: LVPECL conenect

DP83822IF: 100BASE-FX link does not establish despite valid strap and loopback results

Hori Shota
Expert 1415 points

Part Number: DP83822IF

 

Hi team,
 
Purpose
I would like to clarify whether there may be any configuration or setting issues on the PHY side that could prevent 100BASE-FX communication.
Background / Setup
  • We designed a prototype using DP83822IF.
  • We are currently debugging 100BASE-FX communication.
  • Strap configuration has been verified and matches the intended design.
  • The design is based on an existing 100BASE-TX implementation.
Issue
  • 100BASE-FX communication does not work.
Observation
  • Link-up indication via SD signal is confirmed.
  • FX mode is confirmed to be enabled.
  • Loopback testing based on the troubleshooting guide was performed.
  • Loopback results are normal, indicating communication between CPU and PHY is working correctly.
  • Therefore, there does not appear to be a configuration issue between CPU and PHY.
What I tried
  • Re-checked strap settings → confirmed correct.
  • Performed loopback tests → passed.
Assumptions
  • Since the design is based on a 100BASE-TX implementation, some configuration or register settings may not have been correctly adapted for 100BASE-FX operation.
Questions
  • Are there any known differences or required configuration changes when transitioning from 100BASE-TX to 100BASE-FX on DP83822IF?
  • Are there specific registers or initialization sequences that must be adjusted for proper FX operation?
  • Are there any common pitfalls that could cause FX communication failure even when SD and link indicators appear normal?
Best Regards,
Shota
  • 0
    TI__Mastermind 37195 points

    Hi Shota,

    We have a Fiber Debug guide for our ethernet PHYs that may help here. Can you read through this and see if anything stands out in your system?

    Another check I'd recommend is testing your SFP modules and cable with a known-good Fiber platform to ensure the modules and cable are compatible with 100Base-FX.

    Best

    Shane

  • 0 in reply to Shane Hauser
    Expert 1415 points
    Hi team,
    We are using the following optical transceiver and connecting this device from the PHY side:
    LSB2-A3S-PI-N3
    Microsoft Word - LSB2-A3S-Px-N3-V1.3.doc
    According to the document, this transceiver supports only 100Base-BX10-U.
    Our PHY is DP83822IF, which supports 100Base-FX.
    In this configuration, is it correct to assume that communication may not work because the optical transceiver is only compatible with 100Base-BX10-U and not 100Base-FX?
    Best Regards,
    Shota
  • 0 in reply to Hori Shota
    Expert 1415 points

    Shane-san,

    Thank you for reply.

  • 0 in reply to Hori Shota
    TI__Genius 14480 points

    Hi Shota-san,

    We believe the issue is being causes by this fiber module. From the part datasheet, the voltage parameters do not match the TI PHY datasheet requirements. Therefore, either a different fiber module should be used or the necessary steps need to be taken to adjust the voltage IO.

    Best regards,

    Greg

  • 0 in reply to Gregory Kobyakov
    Expert 1415 points

    Hi Greg-san,

    Thank you for reply.

    Purpose
    I would like to confirm the compatibility between the DP83822IF (100BASE-FX PHY) and an optical transceiver, as well as clarify the root cause of the reported voltage mismatch.
    Background / Setup
    • Media converter: SBFTF1029-101 (single SC connector)
    • Internal optical module: OPTOWAY BTR-3520 (single-fiber SMF type)
    • Optical transceiver: LSB2-A3S-PI-N3 (100Base-BX10-U)
    • PHY: DP83822IF (configured for 100BASE-FX)
    The optical-to-electrical conversion is performed inside the optical transceiver (LSB2-A3S-PI-N3). Therefore, I assume that communication should be possible as long as differential TX/RX pairs are properly connected between the PHY and the optical transceiver (with appropriate level matching).
    Assumption
    • There is no issue between the media converter and the optical transceiver.
    • The key interface is the electrical connection between the PHY and the optical transceiver.
    Questions / Concerns
    1. Regarding protocol compatibility:
      Is it correct to say that communication will not work if the PHY is configured for 100BASE-FX while the optical transceiver is 100Base-BX10-U?
      In other words, is there a fundamental incompatibility between 100BASE-FX and 100Base-BX10-U during the optical-to-electrical conversion?
    2. Regarding the comment: “the voltage parameters do not match the TI PHY datasheet requirements”:
      • Is this issue caused by the fact that the DP83822IF does not support LVPECL levels?
      • Or is the root cause related to a mismatch between the electrical interface requirements of the PHY and the optical transceiver?
    3. Root cause clarification:
      Is the main issue here due to:
      • Differences in communication standards (100BASE-FX vs 100Base-BX10-U), or
      • Electrical interface mismatch (e.g., LVPECL vs non-LVPECL signaling)?
    Could you please clarify which factor is the primary limitation in this configuration?
    Best Regards,
    Shota
  • 0 in reply to Hori Shota
    TI__Genius 14480 points

    Hi Shota-san,

    I believe I found a thread that discusses this exact fiber module, please let me know if this clears things up about its use:

     DP83822IF: LVPECL conenect 

    Best regards,

    Greg

  • 0 in reply to Gregory Kobyakov
    Expert 1415 points

    Hi Greg-san,

     

    Thank you for reply.

    Our customer wants a definitive statement that the root cause is the optical transceiver.
    Can we say that communication with this PHY is not possible when it is connected to the 100Base-BX10-U optical transceiver LSB2-A3S-PI-N3, due to a mismatch in standards?
    Best Regards,
    Shota
  • 0 in reply to Hori Shota
    TI__Genius 14480 points

    HI Shota-san,

    As indicated in this thread from above  DP83822IF: LVPECL conenect ,

    Communication is possible with this module, but it would require additional configuration. Otherwise, a 100BASE-FX module will need to be used to avoid this.

    Best regards,

    Greg