On 6 December 2013 12:00, Dwayne Reid <dwayner@planet.eon.net> wrote:

> You are close to what I am talking about but missed the mark just a bit:
> I set the pin to o/p, write that pin to being LO, then turn the pin
> back to i/p and *read* a logic HI on the pin.  Question: what state
> is the pin output latch in now?
>

You mean you are turning the TRIS to read before the latch can store the
new state?

Tamas



>
> My recollection is that the pin is read in the quadrature clock phase
> Q1 or Q2 and the pin latch is written in Q3 or Q4.
>
> dwayne
>
>
> >Matt Pobursky
> >Maximum Performance Systems
> >
> >On Fri, 06 Dec 2013 11:19:43 -0700, Dwayne Reid wrote:
> > > Good day to all.
> > >
> > > I've been a long-time PIC programmer and thought that I knew all ther=
e
> > > was in regards to Read-Modify-Write issues with early PICs (12-bit an=
d
> 14-
> > > bit core devices).  But I'm doing a re-write of an old project and ra=
n
> > > into a question that I don't have an answer for.
> > >
> > > The situation is this: PIC pin is set as output and is low.  Now I tu=
rn
> > > the pin into an input and read the level on the pin.  This level migh=
t
> be
> > > HI or LO.  Now I turn the pin back into being an output.
> > >
> > > Question is: what is the (output) level on the PIC pin *if* the level
> had
> > > been HI when the pin was read?
> > >
> > > In other words, pin output latch used to contain a logic LO.  The pin
> was
> > > turned into an input and read a logic HI.  Does the pin output latch
> > > update to reflect the level that was read when the pin was an input?
> > >
> > > My gut says that the pin output latch *does* change from LO to HI.
> > >
> > > Any thoughts?
> > >
> > > dwayne
>
>
> --
> Dwayne Reid   <dwayner@planet.eon.net>
> Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
> (780) 489-3199 voice          (780) 487-6397 fax
> www.trinity-electronics.com
> Custom Electronics Design and Manufacturing
>
> --
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>



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