> So, from
> then on, I used six variables in the lcd.o object file which would be
> defined in the main.o file. (the idea behind this is to be
> able to change the ports and bits used by the LCD, depending on the
> complexity or needs of the project.)
>
> So I defined:
> LCTRL -> The port which has the LCD control lines (RS, RW, EN)
> LBUS   -> The port which holds the LCD data/address
> LBUST -> LBUS direction control (LBUS's TRIS register)
> RS -> Bit n: for the RS line
> RW -> Bit n: for the RW line
> EN -> Bit n: for the EN line.
>
> The problem is that I can assign the registers in main.o, but
> not the bits!!

Dave Dilatush replied

>Ricardo,
>
>I've run into this same problem, which is that constants defined
>in one .asm file (with the #define directive) cannot be declared
>GLOBAL as can be done with variables.
>
>The solution I arrived at was to #define bit assignments and
>other global constants in a separate "global declarations" file,
>and then #include that file at the beginning of each .asm file of
>the project.  The global declarations file also contains the
>#include directive which brings in Microchip's processor
>definitions file (for instance, p16f877.inc).
>
>That way, I can change bit assignments, and even the target
>device for a project, by editing only one file instead of editing
>every .asm source file.

This is exactly what is done with Olin's development environment. There is a
global include file where all the port and bit assignments are set up, and
then he has a pre-processor which sets up macros making the assignments a
lot easier to use. In one assignment statement macros for the port, bit and
tris register are all set up together.

See http://www.embedinc.com/pic/ to download the software, and follow the
link there to Jan-Eriks site for a good PDF manual to it all.

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