• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 33 subscribers
  • Views 1114 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DS100KR401: Questions regarding the operation of DS100KR401 in certain applications

Michael Nycz
Intellectual 835 points
Part Number: DS100KR401
Other Parts Discussed in Thread: TLK10232, DS100KR800

I am using the DS100KR401 in the following path....

                                                                                                                        Fiber

SBC with 10G-KR port <----> DS100KR401 <---------> Optical Transceiver <---------> Optical Transceiver <---------> TLK10232 ------------> XAUI port on SBC

I am unable to achieve a 10G link between the 10G-KR port and the effective KR port on the TLK10232. Now, on the TLK10232 we have auto-negotiation and link training turned off. In a previous application of the TLK10232 we were told by TI that we should disable these features. We did not get a thorough explanation of why we needed to turn them off. However, we disabled these features and were able to get the link to work. In the path shown above, the SBC/10G-KR port has auto-negotiation and link training enabled (and are not easily disabled). My question is, do we need to have auto-negotiation and link training disabled on the 10G-KR port in order to be able to link on the TLK10232 when passing through the fiber path described above?

Also, specifically for the DS100KR401, when the MODE is chosen as 10G vs 10G-KR,

1) what specifically does that imply?  Also, is the MODE pin recognized regardless of the state of the ENSMB pin?

2) If the DS100KR401 is in 10G-KR mode the datasheet says....

"When operating in 10G-KR mode, the DS100KR401 transparently allows the host controller and the end point to optimize the full link and negotiate transmit equalizer coefficients as defined in the 802.3ap standard. This seamless management of the link training protocol ensures guaranteed system level inter-operability with minimum latency."

 Does this mean that any writes to the registers are ignored and the DS100KR401 sets the EQ,VOD,DEM values based on negotiation with whatever -KR device it is connected to? Or is it just passing the information between the input of the DS100KR401 to the output transparently?

3) If the DS100KR401 is part of the training process, and a link is never established, does this mean that it was unable to find a set of settings that allowed it to link?

4) When we tested hardware here, we connected to the DS100KR401 using OTS media converters (not 10G_KR specifically). When we are using a non-10G-KR compliant data stream, what will the DS100KR401 do if set to 10G-KR mode.

We are trying to debug hardware so any help in these areas would be greatly appreciated. If you have any questions about the exact set up please post here and I will address them.

Thank you,

Michael Nycz

 

  • 0
    TI__Mastermind 43795 points

    Hi Michael,

    Optical connections cannot convey the analog link training information.  Unless you have a special 10G-KR capable optical module, link training could not be supported.

    Also, specifically for the DS100KR401, when the MODE is chosen as 10G vs 10G-KR,

    1) what specifically does that imply?  Also, is the MODE pin recognized regardless of the state of the ENSMB pin?

    (Lee) Yes, the MODE pin is prioritized above the SMBus register/ENSMB pin by default. The MODE pin can be overridden using SMBus register writes if needed.

     If the DS100KR401is in 10G-KR mode the datasheet says....

    "When operating in 10G-KR mode, the DS100KR401 transparently allows the host controller and the end point to optimize the full link and negotiate transmit equalizer coefficients as defined in the 802.3ap standard. This seamless management of the link training protocol ensures guaranteed system level inter-operability with minimum latency."

     Does this mean that any writes to the registers are ignored and the DS100KR401 sets the EQ,VOD,DEM values based on negotiation with whatever -KR device it is connected to? Or is it just passing the information between the input of the DS100KR401 to the output transparently?

    (Lee):  The DS100KR401 does not negotiate with the other 10G-KR transceivers.  It will maintain the EQ/VOD/DEM configuration settings during the negotiation.  The DS100KR800 non-limiting output characteristics allow analog qualities of the waveform to pass through so the receiver controlling the negotiation can make proper decisions about how to optimize the equalization coefficients of the 10G-KR Tx driving through the DS100KR401.

    3) If the DS100KR401 is part of the training process, and a link is never established, does this mean that it was unable to find a set of settings that allowed it to link?

    (Lee):  Yes if the link is not established then the combination of static DS100KR401 settings and the link training negotiation was not able to develop a viable solution.  In some cases reducing the DS100KR401 equalization and de-emphasis settings will allow a more consistent negotiation.

    4) When we tested hardware here, we connected to the DS100KR401 using OTS media converters (not 10G_KR specifically). When we are using a non-10G-KR compliant data stream, what will the DS100KR401 do if set to 10G-KR mode.

    (Lee): Running the D100KR401 in 10G-KR mode will not make a huge difference in the transmitted waveform.  Switching between KR mode and non-KR mode should highlight a more consistent output voltage since the transmitter voltage gain has been increased.  In either case, the DS100KR401 will equalize and re-transmit the incoming data.

    Regards,

    Lee

  • 0
    Intellectual 835 points
    Lee,
    Thank you so much for your response. Would the same apply to auto negotiation? Meaning will the auto negotiation handshaking be stopped by introducing an optical section in the data path (similar to link training)?

    Mike Nycz
  • 0 in reply to Michael Nycz
    TI__Mastermind 43795 points

    Hi Mike,

    Yes link training like that found in 10G-KR and SAS-3 cannot be completed over an optical connection.

    Regards,

    Lee