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RMII support on RM48L950 / RM48L952 and TMS31LS37

Christopher Gibson1
Prodigy 150 points

Other Parts Discussed in Thread: TMS570LS3137, HALCOGEN

Could someone please clarify if the mentioned Cortex-r4f microproccessors support RMII mode for their Ethernet.

(I have already found a partial answer WRT the TMS570LS3137 on another forum, but I would like to seek further clarification {http://e2e.ti.com/support/microcontrollers/hercules/f/312/t/248196.aspx}).

The data sheets for the mentioned processors does not mention RMII mode, or the multiplexing options for these chips, but the technical reference manual, the HalCoGen code generator, and the HDK's for the devices do suggest RMII support.  I have found no mention of RMII in any of the chip errata.

Could you please clarify the issue surrounding RMII, and the potential remifications for a design where RMII is being used.  I like others before me assumed that the lack of reference to RMII in the data sheet was just accedental ommision, but as explained in the thread above the ommision was purposfull because "we need to wait for full timing characterization over process corners to confirm support".

Thanks in advance

Chris Gibson

  • 0
    TI__Guru 69070 points

    Chris,

    All of the Hercules products with ethernet today include RMII.   But not all of the products have yet been characterized as meeting the RMII timing requirements.  This is mainly an issue with RM48 and TMS570LS31xx, 21xx.    RM46 and TMS570LS11xx are clean.

    If you don't see RMII referenced in the datasheet - no timings, no pinout information,  then RMII on that product isn't supported.

    I can tell you we are about to release a datasheet for Revision C silicon of the RM48 and the TMS570LS31xx that does show RMII as available.   RMII timings were fixed on this revision of silicon so it can be used.   RMII exists on Rev A and B but if you use it there is some chance it may not work because we don't meet the required timings.  Now to be clear, we don't meet the timings in the sense of 'across process, voltage, and temperature with high yield'.   It is most likely that any development kit you have with Rev A and B will work fine in RMII mode.  But we can't advise that you build a product for volume production with these revisions using RMII.

    Hope that makes sense.  Let us know if you have additional questions.

    Best Regards,

    -Anthony

  • 0 in reply to Anthony F. Seely
    Prodigy 150 points

    Hi Anthony.

    Thank you for your clear, no-nonsense reply.

    May I suggest that you add an errata item with respect to the issue, for the earlier silicon versions, so that others don't follow in my folly?

    Best regards,
        Chris Gibson

  • 0 in reply to Christopher Gibson1
    TI__Guru 69070 points

    Hi Chris,

    Thanks. It is a good suggestion given that we have conflicting information with respect to RMII support.  The datasheet rules in the end, but you're right there is enough information out there to make one suspect we missed this and it's a datasheet error.

    The way errata get generated is complex unfortunately and I'm not sure we can get this into the errata, but it really should be so I'll give a shot at running the request up the chain.

    Thanks and Best Regards,

    Anthony