>-----Original Message-----
>From: Peter Onion [mailto:ponion@ALIEN.BT.CO.UK]
>
>> At the moment I am initiating a conversion by hitting a
>button on the
>> PC and then looking at the result. The problem only occurs
>when I set
>> the A2D to use its internal Vref. If I set it to use an
>external Vref
>> and supply 5V and Gnd to the respective pins, I get the correct
>> result.
>>
>
>I could be totally missing the point here, but looking at the
>data sheet I think the internal reference in only 3v ?  So
>inputs greater than this give f.s.d. (0x3f) I think.
>
>(Flame suit on)  ;-)
>
>Peter

There is no internal reference per se.  The A/D converter either uses the
supply rails as the reference, or external voltages applied to the Vref+ and
Vref- pins.

Regards

Mike




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