Crystal oscillator problems on a 16f628a

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  1. - 16th February 2009, 10:38 #1
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    sayzer
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    Quote Originally Posted by Joe S. View Post
    You are sure the config statement is set to HS_OSC, Yes?
    In addition to Joe's,

    Not all 16f628A chips work at 20Mhz. You MUST make sure its type is 20Mhz.

    Also, 15pf instead of 22pf for 20Mhz has always been better in my applications.


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  2. - 16th February 2009, 12:10 #2
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    Hi,

    If it is an existing board ... I'd first carefully clean all the "touched" PCB , verify all Pic pins are correctly soldered ( Laugh, ... who never forgot a pin ??? ) and no short ...

    Magnifying glass required ...

    Then, if no success ...Try you chip on a breadbord with the ol' famous "Blink" program ... you'll know if it is OK. and
    where to look at ...

    Alain

    PS: 4 Mhz chips are not supposed, but work really fine up to ... 28 Mhz !!! ( no µchip warranty ... of course ...)
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