[time-nuts] Why these Crystal Frequencies?

Magnus Danielson magnus at rubidium.dyndns.org
Thu Dec 15 13:32:52 EST 2011


On 12/15/2011 04:13 AM, 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:

> 12.288

AES/EBU and S/P-DIF baud-rate for 96 kHz sampling-rate

128 x 96 kHz = 12,288 MHz

Also in wide use for audio-boards.

6,144 MHZ
24,576 MHz

is related multiples for 48 kHz and 192 kHz.

> 19.44

SDH/SONET STM-1 byte-rate

270*9*8 kHz = 19,44 MHz

51,84 MHz
155,52 MHz
311,04 MHz
622,08 MHz

are related multiples that occurs regularly

Cheers,
Magnus




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