> >No, no, no!  You have to worry about PCLATH whenever you do a CALL or
GOTO
> >to a location that could be on a different page.  After a subroutine
> >returns, PCLATH is set the way the subroutine left it, which is usually
> >pointing to its page.  This can mess up GOTOs that otherwise go to
> >addresses
> >known to be on the same page.
>
> This is odd because I have programs that call subroutines at the very end
of
> a 2K PIC from the ISR routine at ORG 4 with no trouble.  I don't save
PCLATH
> and never adjust it in the program.  The only trouble I run into is when I
> do a computed GOTO jump, in which case I set the PCLATH manually.
>
> If your statement is true, I'd never be able to return to nearly 80% of my
> calls, since they run the gamut of program memory locations from 0x00A
> through 0x700.  Yet I have no problems.

Not odd at all because everything you mention is within the first code page,
from 0 to 7FF.  You won't get away with ignoring PCLATH if your code is on
multiple pages.  You will also have to save/set/restore PCLATH in the
interrupt routine if you do any GOTOs or CALLs in it anywhere.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olin@embedinc.com, http://www.embedinc.com

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.