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piccolos sharing clock

Max Sonnaillon
Intellectual 600 points

Hello,

I am designing a board with more than one Piccolo (28069), probably 3 of them.

I'm thinking in sharing the clock signal among the 3 processors. One would have the internal crystal-oscillator enabled and the other two would be using the external oscillator signal coming from the first one.

It would save me 2 set of crystals + caps, and all 3 DSCs would be perfectly synchronized.

Is there any reason this could cause problems?

Thanks,

Max

  • 0
    Genius 5885 points

    Hi Max,

    As I don't have any real experience in clock distribution, I would rather take external oscillator and feed it to all three devices. Through buffers of course.

    Doing it your way, I would expect problems with "master" picollo as "slave" picollos will change the impedance load on "master" oscillator. At least you should use XCLOCKOUT and not X1 or X2 pins.

    But you should get more knowledgeable opinion from someone that has experience in this field

    Regards, Mitja

  • 0 in reply to Mitja Nemec
    TI__Genius 17291 points

    Max,

    I don't have practical experience doing this, but I would recommend clocking all three using an external canned oscillator.  The devices will not truly be sync'd if you try to use the XCLKOUT from one DSC to clock the others and enabling XCLKOUT can cause additional noise to the system, particularly the analog.

    Some other concerns are pointed out in this thread: http://e2e.ti.com/support/microcontrollers/tms320c2000_32-bit_real-time_mcus/f/171/p/212139/752152.aspx#752152

    Perhaps someone from the community who has actually done this will share their experience.