On Thursday 25 October 2001 08:35 am, Bob Blick wrote:

> Look at what is actually connected to RA4 and decide for yourself. There's
> an N-mosfet and an input buffer. The mosfet is not going to be bothered by
> 14 volts, so the input buffer is the only question mark. Have Microchip
> changed the design of the input buffer from the 16C71 and 16C84 to the
> 16F84? Sure they've shrunk the die, but have there been changes that would
> lower the maximum voltage?

Referring to the 16F84 datasheet,
http://www.microchip.com/download/lit/pline/picmicro/families/16f8x/30430c.pdf
, the indication is that the RA4 pin shares the same input buffer as the
/MCLR pin (its leakage and Vih voltage specs are the same). So I'd guess that
the protection diodes on the standard ports are missing on this pin. They are
apparently missing on the /MCLR pin, because of the warning about latchup due
to voltages below VSS. I wonder if the same warning applies to RA4 (that is,
should you use a series resistor to limit current from negative spikes when
using it as an output?).

--
Ned Konz
currently: Stanwood, WA
email:     ned@bike-nomad.com
homepage:  http://bike-nomad.com

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics