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DS250DF230: Method for discriminating two input data

Yuta Nishie
Genius 4955 points
Part Number: DS250DF230

Hi,

First, let me explain my customer's situation.

<Customer's Situation>

The customer inputs signals at two different rates: 4.9152Gbps and 9.8304Gbps. In order to enable CDR locking of 4.9152Gbps and 9.8304Gbps signals, the customer has configured 4.9152Gbps and 9.8304Gbps data rate in manual mode. 

So when the 9.8304Gbps signal is input, the 9.8304Gbps setting will be CDR Lock, but the 4.9152Gbps setting will be CDR not Lock. This is the behavior the customer expected.

But when the 4.9152Gbps signal is input, the 9.8304Gbps setting will be CDR Lock, but the 4.9152Gbps setting will be CDR Lock. The customer did not expect two types of signals to be CDR locked.

Therefore, the following operations are performed to determine which signal is being input.

・<When input 9.8304Gbps> Lock at 9.8304Gbps → Don't Lock at 4.9152Gbps → Lock at 9.8304Gbps → Determine 9.8304Gbps

・<When input 4.9152Gbps> Lock at 9.8304Gbps → Lock at 4.9152Gbps → Determine 9.8304Gbps

<My Question>

Is it possible to determine that 9.8304Gbps has been input by the following method?

＊The figure below does not take into account the delay time.

Best Regards,

Nishie

  • TI__Mastermind 27910 points

    Hi Nishie-san,

    I don't expect this method to work to distinguish between 9.8G and 4.9G data for 2 main reasons.

    1. Depending on the pattern transmitted, I expect the retimer can lock to 9.8G input data when the CDR is configured for 4.9G. I believe the customer has observed this behavior as well, as described in this E2E thread: https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1300746/ds250df230-behavior-when-signals-of-different-data-rates-are-input
    2. Transitions between raw and retimed output data will not be seamless. In raw data mode, the signal will still pass through CTLE and VGA blocks which will distort the signal.

    Note that Monday and Tuesday are US holidays. I can continue supporting if there are any follow-up questions on Wednesday 12/27.

    Best,

    Lucas

  • in reply to Lucas Wolter
    Genius 4955 points

    Hi Lucas-san,

    Thank you for your support.

    The attached image was deleted because it was not possible to post the waveform on E2E.

    Also, I understand that the attached method does not work.

    I would like to contact you directly, so could you tell me your email address?

    Best Regards,

    Nishie

  • in reply to Yuta Nishie
    Genius 4955 points

    Hi Lucas-san,

    In addition to what I want to talk about in the email, I want to confirm something.

    3) Does your answer to (1) explain that there is a possibility to lock all of the items shown below?

    4) Also in customer's system, the retimer can not lock to 9.8G input data when the CDR is configured for 4.9G. Is there an internal function (hidden register) to prevent locking when a half/double rate is input?

    5) If yes at (3), is there a way to determine whether the input data is 4.9G or 9.8G?

    Best Regards,

    Nishie

  • in reply to Yuta Nishie
    TI__Mastermind 27910 points

    Hi Nishie-san,

    Yuta Nishie said:
    3) Does your answer to (1) explain that there is a possibility to lock all of the items shown below?

    Yes that is my expectation.

    Yuta Nishie said:
    4) Also in customer's system, the retimer can not lock to 9.8G input data when the CDR is configured for 4.9G. Is there an internal function (hidden register) to prevent locking when a half/double rate is input?

    In the following E2E thread, you described the customer seeing CDR lock to 9.8G input data while configured for 4.9G. Is this no longer the case?

    https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1300746/ds250df230-behavior-when-signals-of-different-data-rates-are-input

    It is not possible to prevent locking to half/double rates with protocol unaware retimers. The retimer cannot tell if the data rate is half-rate or full-rate based solely on the data signal received.

    Yuta Nishie said:
    5) If yes at (3), is there a way to determine whether the input data is 4.9G or 9.8G?

    It is not possible to determine if input data is 4.9G or 9.8G using only the retimer. If possible, I suggest that the customer uses some other method within their system to determine if data is 4.9G or 9.8G, and use this information to change the divider setting on the retimer.

    In HSSC we are expected to handle all customer support communication through E2E. If you would like to share information/ask questions privately, you can send me a private message through E2E. I sent you a friend request.

    Best,

    Lucas

  • in reply to Lucas Wolter
    Genius 4955 points

    Hi Lucas-san,

    Sorry, My explanation in another E2E thread was incorrect. The following conditions are correct in the customer's system.

    The retimer can not lock to 9.8G input data when the CDR is configured for 4.9G. Also the retimer can lock to 4.9G input data when the CDR is configured for 9.8G.

    I contacted you by private message. I would appreciate it if you could reply.

    Best Regards,

    Nishie

  • in reply to Yuta Nishie
    TI__Mastermind 27910 points

    Hi Nishie-san,

    Thank you for the clarification. I will message you privately.

    Best,

    Lucas