> Thanks for the spread sheet (Brent) and the formula (Jinx).
> Till I can get a different crystal purchased and installed (actually
> I'm using a Murata resonator I might have to change a foot print on
> my board). I wanted to use my 4MHz crystal but when I set the BRGH
> 1(Low Speed) and run through the math I end up with a %8.51 error.
> Can anyone tell me if that is close enough to work for now so I can
> test my code?

That's quite a long way off and almost certainly won't work. Work on more like 2% 
worst case max. The spreadsheet has a list of some popular crystal freqs in the left 
most column, those with * next to them will give accurate baud rates. If you ditch 
your 4MHz crystal and substitute with 3.6864MHz you can get precisely 115200 
baud with SPBRG = 1 and BRGH = 1.

The only annoying thing with such "odd" crystal frequencies is that it makes other 
timing tasks seem slightly more awkward, eg. with 4MHz osc it's nice to know that 1 
instruction = 1us.

-- 
Brent Brown, Electronic Design Solutions
16 English Street, St Andrews,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: 027 433 4069
eMail:  brent.brown@clear.net.nz


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