Thomas wrote:

> I have a simple device built with a 16C73A.
> I read two channels of the A-D, a dual color LED to indicate which
> channel,
> do a table lookup, and write a byte to Ports B and C.
> (Resistor ladder D-As)
> The whole system works.... mostly.
>
> When the voltage to the A-D gets to 4.06 volts the PIC freezes.
> If I lower the input to 4.05V (or lower) it resumes.
> This happens on either channel.
>
> I have noise filtered each A-D channel, which helped slightly.
> (It used to freeze at 3.9 volts.)
> My 1 Ghz scope shown no noise peaks over 1 mv. at 4.06 volts.
>
> I selected VCC (+5) as the reference for the A-D.
>
> All of this suggests I'm sending voltages over the reference limit,
> but I'm at a loss to see how.
>
> Does anyone have any ideas?
>
> Did I miss some critical parameter in the specs?
>
> What is the airspeed of an unladen swallow?
>
African or European?