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AM335X EFUSE MAC IDs, always valid?

Michael Williamson
Expert 1925 points

Hi,

We are developing a system on module (SOM) based on the AM335x CPU and had a question related to the MAC addresses (in EFUSE) of the CONTROL_MODULE (offsets 0x630 through 0x63C) .  The TRM specifies that these are "device-dependent" and doesn't say more more on the subject.   The units we have show valid MAC address (with a TI registered OUI of  D4-94-A1).  Does TI guarantee that all AM335X devices will have pre-assigned, unique, valid MAC addresses assigned to each unit?

The linux and u-Boot code tries to read these values first, and if they are invalid, will use numbers pulled from external FLASH on the EVMs.  It's not clear if this should really be necessary.

For other SOMs, we have typically registered for and assigned our own MAC addresses to devices capable of ethernet communication.  We are trying to determine if we need to do that for this design.  If TI always provides valid, unique MAC addresses at factory, then we can skip this registration (and not waste address registration space as well as $$ in the assignments).  Can someone confirm this is a valid assumption?

Thanks.

-Mike

  • 0
    TI__Guru 74610 points

    Mike, yes these MAC IDs will be unique for each device.  Initial samples of silicon did not have these eFuses blown, thus we had a backup plan of reading the MAC IDs out of the flash.  But in general this should not be necessary.  All devices will have the first  2 MAC IDs programmed, and some (ZCZ package supporting ICSS) will have the 3rd programmed.

    Regards,

    James

  • 0 in reply to JJD
    Intellectual 360 points

    Hi Mike,

    Thanks for the information, I am also looking for same MAC ID programming solution for AM335x

    can you please confirm the following

    1. all AM335x series of processors comes with eFuse support with valid mac address (unique) ?

    2. user no need to place separate prom or other mechanism to maintain mac address ?

    thanks & regards

    Nagendra

  • 0 in reply to nagendra bankupalli
    TI__Guru 58515 points

    All production AM335x devices provide at least two unique valid MAC addresses.

    As James mentioned, some AM335x contain more than two MAC addresses.  The two MAC addresses programmed in a specific AM335x device represent the lowest  and highest MAC addresses assigned to that device.

    The user only needs to use an external non-volatile memory device for MAC addresses if they do not want to use the MAC addresses programmed in the AM335x device.

    Regards,
    Paul

  • 0 in reply to JJD
    Intellectual 405 points
    Hi James, E2E: What registers would be used to store the 3rd programmed MAC address, if supported? Thanks, ...doug
  • 0 in reply to Doug Kehn
    TI__Guru 58515 points

    A third register is not required.

    The two values stored in the two registers represent the lower and upper MAC addresses assigned to a device. For example, a device assigned two MAC addresses will have two consecutive values stored in these two registers. A device assigned three or more MAC addresses will have two values that are not consecutive.  In the case where the values are not consecutive, all values between and including the upper and lower values represent MAC addresses assigned to the device.

    Regards,
    Paul 

  • 0 in reply to peaves
    Intellectual 405 points

    Hi Paul,

    Thanks for the explicit explanation.  I should have gathered this from your earlier post: "The two MAC addresses programmed in a specific AM335x device represent the lowest  and highest MAC addresses assigned to that device."

    Thanks,
    ...doug

  • 0 in reply to JJD
    Prodigy 50 points

    Hi James,

    can you tell me, where the 3rd address is stored, if ICSS is supported?

    There are CONTROL_MODULE mac_id[1:0]_[hi:lo] registers, but where are is the analogous ICSS register?

    Besides I realized, one address is allways skipped between mac_id0 and mac_id1. I.e. A0:F6:FD:4D:2E:CA and A0:F6:FD:4D:2E:CC, A0:F6:FD:4D:2E:D6 and A0:F6:FD:4D:2E:D8 and so on. Can you assure, that the skipped address is also unique and can be used for other purposes? (We need overall 4 unique MAC IDs for Ethernet and PROFINET via ICSS.

  • 0 in reply to Joachim Hofmann
    TI__Mastermind 43691 points
    Dear Mr. Hofmann,

    it is not a good idea to piggy back on old threads as they may get missed. Better to open a new one and reference old one if needed.

    As said above there is a range of MAC IDs programmed into AM335x (independent of device number as far as I know) by low and high values with one skipped as you realized. So we provide 3 MAC IDs that are reserved/unique and taken from a TI pool. If you need more (or have the device recognized as assigned to your company) you need to use your own MAC pool.

    regards,