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DP83822I: Reducing Time from Cable Connect to Data Start

Darren (FAE)
Expert 5483 points
Part Number: DP83822I


I have a customer considering the DP83822 in a design.
They want to be able to reduce the time from a cable-connect event, to when data starts transmitting.

The below is a general understanding of how to do this:
- Disable Auto-MDIX; or Enable Fast-Auto-MDIX
- Disable Auto-Negotiation; or Enable Fast-Auto-Negotiation

From the DP83822 DS, it looks like both Fast-Auto-MDIX and Fast-Auto-Negotiation features are supported by the device.

Questions:

Could you give a general estimation of the expected reduction in time ("n" ms reduction, etc) for the following approaches?

1) Auto-MDIX and Auto-Negotiation are disabled
2) Fast Auto-MDIX is enabled; Auto-Negotiation is disabled (if enabling Fast Auto-MDIX, understanding is Auto-Negotiation needs to be disabled)
3) Auto-MDIX is enabled; Auto-Negotiation is disabled
4) Auto-MDIX is disabled; Fast-Auto-Negotiation is enabled
5) Auto-MDIX is enabled; Fast Auto-Negotiation is enabled

Or, if there is no time reduction due to the combinations listed above - what would be the expected reductions for changing the following parameters?

a) Auto-MDIX = disabled
b) Fast-Auto-MDIX is enabled
c) Auto-Negotiation is disabled
d) Fast-Auto-Negotiation is enabled

*For me, any help/advice on implementing such time-saving techniques, in addition to the above, would be much appreciated.*

Regards,
Darren

  • 0
    TI__Mastermind 40225 points

    Hello Darren,

    The fast way to reduce the time from a cable connect to data transmittal would be disabling auto-MDIX and auto-negotiation, but without enabling the fast versions of them. 

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    TI__Expert 5483 points

    Hi Gerome,

    Thanks for the feedback.

    Do you have any documentation that gives an example of a setup using the different configurations, and has some reference numbers on the reduction in link time and/or tradeoffs?

    Darren

  • 0 in reply to Darren (FAE)
    TI__Mastermind 40225 points

    Hello Darren,

    Linkup times will always be dependent on a myriad of variables within the system, such as cable quality, etc. What is the purpose of this inquiry? What is the use case?

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    TI__Expert 5483 points

    Hi Gerome,

    I updated the use-case info in the "Notes" section - please see.

    Basically, the engineer wants to pick the best setup to achieve the fastest link time. 

    I understand that the time reduction is dependent on multiple system-level variables, and it is difficult to provide a time-reduction estimate.

    At the very least, could you rank the following setups in order of fastest-linkup to slowest-linkup?

    1) Auto-MDIX and Auto-Negotiation are disabled
    2) Fast Auto-MDIX is enabled; Auto-Negotiation is disabled (if enabling Fast Auto-MDIX, understanding is Auto-Negotiation needs to be disabled)
    3) Auto-MDIX is enabled; Auto-Negotiation is disabled
    4) Auto-MDIX is disabled; Fast-Auto-Negotiation is enabled
    5) Auto-MDIX is enabled; Fast Auto-Negotiation is enabled

    Thanks,

    Darren

  • 0 in reply to Darren (FAE)
    TI__Mastermind 40225 points

    Hi Darren,

    The order you have listed is the order from fastest to slowest, according to our estimates. Please keep in mind that with in option 2, robust and regular auto-mdix need to also be enabled. Option 3, robust auto-mdix also needs to be enabled. Please keep in mind that this is theoretical, and that these configurations have not been tested, so a bench validation would be needed on the customer side.

    Sincerely,

    Gerome