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Kinetis K64 in RMII fixed 50MHz mode; Multilink FX speed is ..?
Gary O. Jun 24, 2015 at 12:38 PM (12:38 hours)
Staff: Edison T.

  • Hi --

    So the problem with my Kinetis K64FX512 board that you were so helpful with last week turned out to be a lack of any clock signal. Fixed that. There are still other problems, but it now won't connect 2/3 of the time, instead of 99.9%. This is with a 25MHz external clock signal. Not great, but good enough to keep debugging the hardware.

    What we really need to do is run in RMII mode, meaning a fixed 50MHz clock, and bypassing both the FLL and PLL. That means that the system clock is 16.6MHz, and some peripherals are running as slowly as 8.3MHz.

    I am getting a "P&E Connection Assistant" dialog box, and so far have not been able to find a BDM Shift frequency setting that it is happy with. Is there one? What minimum system clock rate can the Multilink Universal FX deal with?

    I was also looking at the GDB Server, but aside from downloading code, it's hard to say what it does.


    • Hi Gary,

      The only requirement is that the Shift Frequency cannot exceed roughly 1/5 of your processor's bus frequency (which is usually core frequency divided by 2). This means that there is generally a range of Shift Frequencies that will work.

      Currently, the slowest Shift Frequency for the Multilink Universal FX is about 780KHz. This should support processor bus frequencies greater than 3.9MHz (or core frequencies greater than 7.8MHz).

  • Hummm.. so with a bus frequency of 16 MHz, the problem is elsewhere... 

    OK, thank you very much.

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