Peter wrote:

>On Wed, 4 Jan 2006, Jinx wrote:
>
>  
>
>>Does it matter which capacitor (the one on OSC1 or OSC2)
>>is variable to trim the crystal frequency ? I've looked in all the
>>MChip oscillator pdfs I can find but they don't say. Maybe it
>>doesn't matter or maybe they left it out
>>    
>>
>
>The one on OSCin does the trick. The other one also works but it is 
>different.
>
>Peter
>  
>
A client of mine would adjust his Hitachi HD64180 oscillator with a 
variable cap of 0-10pF in
parallel with a fixed value (probably another 10pF), but he used a 
specially-cut crystal
(NOT AT cut). Alas, he had a heart attack. I never saw his crystal spec. 
but I believe it
was a "parallel cut" of some sort. The freq was nominally 6.144Mhz.

It kept excellent time, about 1/2sec/day.

All I did on that project was write the firmware.

--Bob



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