MCH wrote:
> Am I reading the PIC 18F4520 docs correctly that you can only assign 
> analog inputs in ascending order? IOW, if I want only three analog 
> inputs, I have to use pins AN0, AN1, and AN2 and I cannot make the 
> selection based on open pins such as AN3, AN8, and AN9?
>
> Put another way, if I want AN5 to be analog, AN4-AN0 has to be analog as 
> well.
>   
Yes and no

Yes you can only put pins into analog mode in order. However afaict the 
only thing that putting a pin in analog input mode does is disable the 
digitial input buffers.

So you can still use a pin as a digital output when it's set as analog 
(this was very useful when I had to drive a resistive touchscreen) and 
if you are prepared to put up with the extra power consumption caused by 
having a digital input floating between the rails you can use a pin as 
an analog input when it's set as digitial.
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