Sean Breheny wrote:
> Looking at PIC datasheets, the 16F88 and older PICs have +/-5% INTRC
> osc tolerance over V and T range. Some of the 18F series, though, have
> +/-2% over the full commercial temp and V range.
>   
With the intosc on a 16f886, running at 8Mhz, according to the 
datasheet, you can expect +-2% over 0 to 80*c, and +-5 across the full 
range.

Usually you can get the baudrate generator (assuming a perfect clock) to 
within 0.16, for common baudrates.

Personally, I've used a crystal on most things.  About the only thing I 
haven't used one on is a 16F886 in an application where I know the 
baudrate of the device it is attached to is *exactly* correct, and which 
I also have a very highly accurate 1Hz signal available that I can tune 
intosc to if necessary (so far it hasn't been necessary to add that to 
the field-upgradeable code - about 2K units over 2 years in an outdoor 
environment, and no reported data corruption to date.).

-forrest
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