At 12:46 PM 20/08/2012, you wrote:
>Using 16f57 for ultra low cost, I can't get the external rc oscillator to =
work
>at all. I can inject clock and CLK2 outputs CLK1/4, but connecting a pullu=
p
>between 2k2 and 10k to CLK1 simply pulls it high and nothing interesting e=
ver
>happens. There is no table for RC selection in the datasheet of the 16f57.=
 I
>could find nothing relevant in the microchip.com search engine. Can someon=
e
>please point me to a table or other data set which clarifies the rc compon=
ent
>limits for modern 16f57s? And other pics?
>
>My current option seems to be trial and error. C is 47pF ceramic for now. =
F
>should be about 1MHz with 10k and 47pF, no? I mean, from plain RC=20
>circuit theory.

Yes, about so. There are some graphs in the 16C57 that might help as a
rough guideline, but there are no guarantees that the F57 will be the
same (which is okay, since IIRC there are no min/max values anyhow).
There's also some general info in the midrange reference manual.

As to your difficulty, are you 100% sure that you have set the configuratio=
n
bits correctly for an RC oscillator?

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the rewar=
d"
speff@interlog.com             Info for manufacturers: http://www.trexon.co=
m
Embedded software/hardware/analog  Info for designers:  http://www.speff.co=
m



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