> My first (unsuccessful) attempt to locate some routines on Page 1 and to
> call them from Page 0 has sent me scrambling for the datasheets and
whatever
> other online resources I could find.  There seems be a variety of
approaches
> to the PCLATH issue, most of which have confused the daylights out of
me.
> Perhaps someday I'll be up to the more sophisticated techniques (macros,
> etc.), but for now, could I not just make every single CALL in my
program an
> LCALL and call it good?

LCALL isn't documented in the MPASM manual I have (DS33014G), although it
may be old.

I strongly recommend that you don't just try to cheap out and make this
project work "somehow" quickly instead of sitting down and learning this
right.  You're going to have to do that sooner or later, and the sooner
you do it the more you will benefit from it and the less messy code you
will have around.  Macros ARE a good way of dealing with this issue, and
the macro language is trivial to learn.  You will find them a powerful
tool with many uses.

The convention I use is that PCLATH is always set for the page the current
module is located in, and modules don't cross page boundaries.  That means
I can use GOTOs and CALLs inside a module without having to worry about
PCLATH.  For calling outside a module, I use my GCALL (Global Call) macro.
It sets PCLATH to the target page, and then does a CALL.  Just as
important, on return it restores PCLATH to the local page.

You also need to think about RAM banks.  Take this first project as a
learning exercise and either write out all the paging and banking
instructions or create yourself some dumb macros to help a little.  After
you've attained a good understanding of paging and banking, then you'll be
ready to look at a bunch of more sophisticated macros I have.  You'll find
a whole PIC development environment at http://www.embedinc.com/pic.  It
handles paging, banking, abstraction of I/O pins, portability between
processors, and a few other things in a nice integrated way.


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