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Variations on XTAL clock frequency

Discussion in 'Embedded' started by Guest, Feb 19, 2005.

  1. Guest

    Phil Allison Guest

    "Phil Allison"

    ** Correction.

    .............. Phil
    Phil Allison, Feb 22, 2005
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  2. Guest

    Stef Guest

    In comp.arch.embedded,
    It's just there because the appnote says to put it there. And it allows
    a demanding customer to calibrate the clock himself if he wants to. ;-)
    Stef, Feb 22, 2005
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  3. ... > [RTC clock drift on a PC ...]

    There are clock correction programs that either apply a daily
    correction to the time or query the NIST clock in Colorado.
    Nicholas O. Lindan, Feb 22, 2005
  4. Guest

    mc Guest

    Do they use crystals that are much lower-grade than even the cheapest RF

    Ceramic resonators, maybe?

    Do they have firmware that is incorrect? Maybe the problem isn't just
    mc, Feb 22, 2005
  5. oops You are right .... dunno how I missed that one ? .. actually looks like
    I forgot to multiply by 100 ..... ;-)
    Richard Freeman, Feb 23, 2005
  6. Guest

    MC Guest

    Who knows ?. Every manufacturer will use what they want at the time.
    It's not a firmware issue, more a situation that the hardware timekeeper
    is not intended to be super accurate and therefore providing things to
    make it more accurate (such as temperature control and accurate
    oscillators) can become expensive.
    MC, Feb 26, 2005

  7. The reason that PC clocks drift is that the crystal
    is cut for a different mode of vibration than most
    higher frequency crystals. To save power, the
    crystal oscillator that runs off of battery in your
    PC operates at 32768 Hz (or something nearby).
    The crystal vibrates in a flexing mode rather than
    the more stable shear modes because that is the
    only way to get the frequency down without
    having to make a truly huge device that would
    require more power to keep going.
    Larry Brasfield, Feb 27, 2005
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