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DP83822IF: Using the DP83822 EVM in Fiber Optic Mode

Magid Fazel
Prodigy 60 points
Part Number: DP83822IF

Hi,

We, at Teledyne, use the DP83822IF in our design. We purchased multiple DP83822 EVM boards. Our design and of course, the demo board work fine in 100BaseT which is what we use. We are now trying to convert our design to support Fiber Optics also.

The Eval board and the manual shows the changes required to change to F/O. To baseline the design, I wanted to make sure the Eval board works in 100Base-FX after making the list of changes. I did the following:

1-converted the Eval board per instructions on sheet 18. I also matched the termination requirements for the SPF transceiver that I am using with PECL logic.

2-Inserted SD-SxAA1-D11 SPF optical transceiver

3-cabled to a "SFP Fiber to Ethernet Media Converter" with the same SD-SxAA1-D11 SPF optical transceiver

4-Power up - I do not see any link indicating that it works.

Q1 - Any idea what could be wrong?

Q2 - Do you offer any eval boards that are already in F/O mode that I just insert a F/O transceiver and see the link to the converter? Just in case the HW MODs to demo board are wrong! 

Thanks

Magid

  • 0
    TI__Genius 15612 points

    Hi Magid,

    Thanks for your query!

    Q1 -

    Please share a register dump if you are able so I may confirm the PHY config. For quick tests to debug, please read link status after writing 0x1F = 0x4000, and test with any other pairs of 100Base-FX SFP modules you have available.

    Q2 - 

    Unfortunately no, although we have an internal EVM configured for F/O that I can provide images of, along with the SFP modules that are working on our end for link.

    Best Regards,

    Evan

  • 0
    Prodigy 60 points

    Hi Evan,

    Thanks for quick response.

    1- I am using your Eval board and I do not communicate (read/write registers) with the board. All I do is power up and assume that it comes up in 100Base-FX. I changed the bootstrap resistors as follows:

    Installed R84 = 6.2K

    Installed R88 = 1.96K

    Should now set COL to mode 3 which enables FX.

    Perhaps I need to set another bootstrap as well?? 

    2-Please provide the SPF module P/N that you are using. Also, please provide any other changes you have make to the board besides the ones listed on page 18. Example - termination, bootstrap, etc. 

    Thanks

    Magid

  • 0 in reply to Magid Fazel
    TI__Genius 15612 points

    Hi Magid,

    This COL strap is correct to enable FX. This can be verified by reading register 0xA[14], where reading '1' is fiber enable.

    One change on our EVM is including R74 (0ohm) for the Signal Detect connection to the Fiber interface - does populating this change the behavior you are seeing?

    I have seen valid communication for these SFP modules:

    1) AXCEN AXFE-1314-0M04 (100FX Class 1, 1310nm)

    2) Avago AFBR-5715PZ (Class 1, 850nm)

    In the case where we have to debug this more thoroughly, do you have access to an MSP launchpad so we may program the PHY externally?

    Thank you,

    Evan

  • 0 in reply to Evan Mayhew
    Prodigy 60 points

    Hi Evan,

    Tried R74 - no link.

    Tried AFBR-5715 SFP module - no link.

    Q1 - Didn't you have to make any changes to the termination resistors? Default termination R37 38, 39, 40 50 OHMs to 3.3V. The SPF module needs 100 OHM termination or LVPECL- not to 3.3V. Correct?

    Q2 - How do you test your setup? I.e. where do you connect the other end of the F/O cable? Do you basically get a link light right away?

    Thanks

    Magid    

  • 0 in reply to Magid Fazel
    TI__Genius 15612 points

    Hi Magid,

    [1] The termination resistors are still default 50ohm on EVM I have tested with. I'm unclear on the appropriate termination for this SFP module, I will check again to see if this termination scheme is working for both Axcen and Avago models.

    [2] We connect the other end of Fiber to a network switch or test equipment for traffic generation/checking. Link typically comes up after setting the other end-point to force 100Base-FX. Writing 0x1F to 0x4000, or replugging the SFP module is occasionally required to update the link status.

    Thank you,

    Evan

  • 0 in reply to Evan Mayhew
    Prodigy 60 points

    Thanks Evan

    Every SPF module including the one you are using shows a single R between RX+/- which is about 100 OHMs. The default has 50 OHM on each leg pulled up to 3.3V. 

    If you have not changed it and it works, I have to try while you check on the termination requirements of SFP vs. the termination on your board.

    Is there an LED on the Demo board that should turn on when the 100Base-FX link is established?

    Magid

  • 0 in reply to Magid Fazel
    TI__Genius 15612 points

    Hi Magid,

    I've verified again link for AXFE-1314-0M04 (100FX Class 1, 1310nm).

    The following steps may help get link up with equivalent modules:

    1) Verify 0xA[14] = '1' for 100-FX mode enable

    2) Write 0x1F = 0x4000 to refresh link status

    3) Re-plug SFP module.

    D4 should light up for Fiber link.

    However, I could not get link with Avago AFBR-5715PZ. Sorry for the confusion here, I believe I mistook the wrong SFP module for link during the previous tests.

    Thank you,

    Evan