Hello Richard,

> I am new to PICs and I emailing concerning the reliability of the 16F628's
> internal oscillator. Is it reliable enough to time the USART or am I crazy
> to even think about it?

    I've made a little cheap device that communicates with the internal
USART of a PIC16F628 using the INTRC, but wouldn't make it again.

    The speed of the INTRC on the F628's I have is more than 5% slower than
the nominal 4MHz IIRC. I had to adjust SPBRG=26 (instead of SPBRG=25) for it
to work at 9600bps and still it's not very confiable.

    I've made some tests to see how the INTRC speed would drift with
temperature and found very little (almost negligible) variation.

    Best to use a XTAL or resonator. If you need more pins, use a PIC16F870
(US$0.60 more expensive than the F628 here in Brazil) and be happy.

    Best regards,

    Brusque

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Edson Brusque                 C.I.Tronics Lighting Designers Ltda
Research and Development               Blumenau  -  SC  -  Brazil
Say NO to HTML mail                          www.citronics.com.br
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