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Original question:

DP83826I: How to configure DP83826 to implement EtherCAT communication

DP83826I: EtherCAT HW strapping

Eduard Kliger
Prodigy 10 points
Part Number: DP83826I
Other Parts Discussed in Thread: DP83826E, DP83826EVM

HI

I considering adding HW strapping to my new design, instead using only SW strapping thru Serial interface.

What advantage HW strapping present kipping in mind that i have location limitations.

What  HW straps should be used for MII interface .

Thanks

Eduard Kliger

  • 0
    TI__Mastermind 39855 points

    Hi Eduard,

    For EtherCAT configurations, we have a great app note for this, SNLA344A. Please take a look at this for detailed support in configurations.

    Regarding HW strapping vs register writing, we offer strapping to set the PHY into specific modes upon every time during reset and powerup. Essentially changing what the "default" state is by setting the PHY to operate a RMII instead of MII (for example). Another use case is if all configurable are handled by bootstraps and SMI (MDC/MDIO) is not possible).

    For you application, depending on the PHY's mode (Basic or Enhanced), multiple straps might be in play to ensure MII mode. Other points be aware of for EtherCAT is FLD strapping, as well as ensuring Odd Nibble Detection via software.

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 10 points

    Hello

    I look at document snla344a - "How and Why to Use the DP83826E for EtherCAT® Applications"

    and to tell you the truth it confused me.

    In figure 3-1 and 3-2: DP83826 is in basic mode( "mode" pin grounded) and configured to address 01h and 07h.

    • Why enhanced mod not being uses? This mode is dedicated for real-time applications like EtherCAT®
    • EtherCAT® requires this straps: Auto-MDIX enabled, Fast link-drop enabled, Auto-negotiation enabled. Why there is no HW straps for this?
    • I see that the straps are turned on with serial interface in "DP83826 register setup" section .  Does this options available in basic mode? If so what is the difference between the basic and enhanced modes?
    • Additional issue I see is with the address. As I remember there is recommendation that the PHY address will be same as ESC port number so the address for most applications should be 00h and 01h.

     

    Pleas your support to figuring this out.

    Thanks

  • 0 in reply to Eduard Kliger
    TI__Mastermind 39855 points

    Hi Eduard,

    I will bring this to the team for discussion. I expect to have a response by 11/30/21 at the latest due to the Thanksgiving Holiday.

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    TI__Mastermind 39855 points

    Hi Eduard,

    There is no risk with putting the PHY in enhanced mode from the start via mode select. As per PHY addresses, you can make the PHY address whatever you would like to by strapping the appropriate resistors on appropriate pins.

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 10 points

    Does RX pins requre sereal resistors (33ohm) or as in the DP83826EVM card no need or the sereal resistor ?

  • 0 in reply to Eduard Kliger
    TI__Mastermind 39855 points

    Hi Eduard,

    There are no need for 33 ohm serial resistors on the MAC lines. You can either put a 0 ohm resistor there for future debug or remove footprint altogether. 

    Sincerely,

    Gerome