• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 1120 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.

DP83867E: Link Drop/ Detect Questions

Richard Elmquist
Mastermind 45250 points
Part Number: DP83867E

I have a customer who is evaluating the DP83867E for their application and they have several questions regarding the operation:

We are evaluating the DP83867E for use in a future application (1000BT) which requires us to understand link drop/detect times. 

Regarding link drop: 

What value is T1 set to and which register is used to set this value? TI is shown in figure 19 on page 34, but no timing information is given for T1 in this diagram.

The datasheet states that in the T1 timer period there are several criteria allowed to generate link loss even and drop the link, including:

1.      Loss of descrambler sync

2.      Receive errors

3.      MTL3 errors

4.      Mean Squared Error (What does this mean? I do not see it defined in the 802.3 spec nor the PHY spec)

5.      Energy Loss 

What exactly would cause the link to drop? For example - would the link drop if only 1 receive error occurred in the T1 time period? If not – how many errors would need to be received during T1 for the link to drop? 

Regarding link detection: 

How long does it take to detect a link, assuming Auto-MIDX and Auto-Negitionation are both disabled? The data sheet mentions a Fast Link Detect feature (section 9.4.6.5), but it does not indicate what the standard link detects times are and what the fast link detect times are.

Thanks for your help with this.

Richard Elmquist

  • 0
    TI__Mastermind 45250 points

    Has anyone had a chance to look at the request above?

    Can you give a time frame as to when you might be able to provide the information?

    Thanks for your help with this!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Mastermind 23675 points
    Hi Richard,

    Fast link drop is a tool to decrease the search window for a poor link. Instead of having about a +200us window, the observation window is reduced to around 10us. When a certain number of issues occur within that window, the device will drop the link.
    For example, MLT3 error will look for 20 errors.

    All the fast link detection options are in relation to use with Auto-MDIO and/or Auto-Negotiation. Please see register 0x1Eh for more details about the different fast link detection tools.

    I do not have data on the speed of link for 1G, 100M or 10M operation. It is difficult to put a min/max value on this because there are many factors that come into play.

    Best regards,
    Ross
  • 0 in reply to Ross Pimentel
    TI__Mastermind 45250 points

    Ross,

    Thanks for your response!

    I will let you know if the customer has any further questions regarding your response.

    Thanks again for your help.

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Mastermind 45250 points

    Ross,

    The customer still has some specific questions that he hopes that you can answer:

    ·        How many receive errors need to occur in the T1 window for the link to drop?

    I am not sure on this one. Does any receive error in the T1 window cause it to drop the link? Can you be specific in your answer?

    ·        What do you mean by: fast link detection options are in relation to use with Auto-MDIO and/or Auto-Negotiation.

    Does this mean that if those features are disabled, the fast link detection does not apply?

    Could you provide a best case scenario for how fast the link is able to re-establish.

    Once again I am not sure of the answer.

    Thanks for your help with this!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Mastermind 23675 points
    Hi Richard,

    When 32 RX_ERs are received within the T1 window the link will be dropped.

    Please read through register 0x1Eh. Within that register you will see what I mean.
    Fast link detection is only used when you have Auto-MDIX and/or Auto-Negotiation enabled.
    By default the features are disabled. You can enable specific ones depending on what you want to use.
    However, it is advised to use TI to TI when enabling them because other link partners might not support such features.

    Best regards,
    Ross
  • 0 in reply to Ross Pimentel
    TI__Mastermind 45250 points

    Ross,

    Thanks for your response!

    I believe that this will answer the customer's questions, but I will let you know.

    Thanks again for all your help!

    Richard Elmquist