On 19/05/2011 04:19, IVP wrote:
> Hi Steven
>
> If you want reliability over the whole voltage and temperature range I
> think INTOSC would be a poor choice. You would have to decide
> if avoiding the small complexity of a crystal/resonator is worth the risk
>
> Within a narrow V and T range INTOSC would be workable
>
> One problem is that the base 8MHz (a 10^x frequency) is not conducive
> with 9600 baud (a 2^x frequency), ie an error is introduced at the divisi=
on
> (Fosc/baud)/64 before even considering INTOSC accuracy
>
> Using Example 20.1 in the datasheet
>
> ((8000000/9600)/64) =3D 13.0208, truncated to 13
>
> 8MHz / 9600 ->  0.16% error @ 25C, 5V, INTOSC accurate. 0%
> error is achieved with 7.987200MHz
>
> (7987200/9600)/64 =3D 13.0000, no mathematical loss
>
Even a resonator often isn't good enough.

--=20
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