[time-nuts] Why these Crystal Frequencies?

Peter Bell bell.peter at gmail.com
Wed Dec 14 23:26:29 EST 2011


Ah, and I just noticed that you had the H-Maser and Rb marked wrong

On Thu, Dec 15, 2011 at 12:17 PM, Peter Bell <bell.peter at gmail.com> wrote:
> 11.0592MHz is another crystal used for accurate baud rates -
> especially on MCUs that had a 12MHz maximum clock (like the Intel
> 8051)
> So is 9.8304MHz - used on a number of Mototola (now Freescale) MCUs
> 17.734475 is 4 times the PAL color burst frequency of 4.433619MHz
>
> I'll see if I can think of anything else.
>
> Regards,
>
> Pete
>
>
>
> On Thu, Dec 15, 2011 at 11:54 AM, Brooke Clarke <brooke at pacific.net> wrote:
>> Hi Rex:
>>
>> Thanks, I had 14.7456 mis listed (off one row) as the 4X CB freq.  I've
>> updated the table.
>>
>>
>> Have Fun,
>>
>> Brooke Clarke
>> http://www.PRC68.com
>> http://www.end2partygovernment.com/Brooke4Congress.html
>>
>>
>> Rex wrote:
>>>
>>> Brooke,
>>>
>>> 14.31818  is 4x the analog color burst (~3.58)
>>>
>>> 18.432   divides cleanly for baud rates. I've used it as a PIC clock for
>>> that. I think some of the others may be too, but I didn't recognize or do
>>> the math to see.
>>>
>>>
>>> On 12/14/2011 7:13 PM, Brooke Clarke wrote:
>>>>
>>>> Hi Pete:
>>>>
>>>> Maybe you can shed some light on the common xtal frequencies table where
>>>> there's no explanation given?
>>>> http://www.prc68.com/I/pdf/Crystal_Freq.pdf
>>>> An answer is not it's an "even" frequency or "it's an even binary
>>>> frequency. That's true for most of these and the factors are part of the
>>>> table above.
>>>> The question is why do they exist?
>>>> such as:
>>>> 32.0 kHz
>>>
>>> ...
>>>
>>>
>>>
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>>
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