Well, the databook for the f877 says that "The maximum recommended
impedance for analog sources is 10K". Does this mean that my pots are
too high? Also, if I only want to use 8 bits of resolution, do I set the
ADFM register to 0, and then just read the result of ADRESH, and forget
about ADRESL?

Thanks,

Josh
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David VanHorn wrote:
>
> At 03:13 PM 11/24/01 -0500, Josh Koffman wrote:
> >Or how about a 250K pot? Would it really make a difference seeing as I'm
> >measuring the relationship between vref and the the analog input?
>
> There's no difference, provided that the chip's input impedance is
> infinite, and there's no interfering EMI.
> Otherwise, you can calculate the effect of non-infinite input impedance.
> EMI is harder to predict, but generally, keeping your source impedance low
> keeps this from becoming much of a problem.

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