Marechiare wrote:
> I did read the datasheet before. It says min logical high is 80% of
> Vdd.

I just looked at the 18F2520 datasheet, DS39631E, as a example.  On page 335
in the section "Input High Voltage", it specifies parameter D041 "with
Schmitt trigger buffer" to have a min/max range of 0.8 Vdd to Vdd.

On a 5V system therefore, any input voltage from 4.0V to 5.0V is guaranteed
to be interpreted as a logic high.

> I did find no clause that it guarantees any level higher to be
> interpreted as high;

Actually that's exactly what it's saying.  Read it again.


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