>     ... and then, later in your code, you mistakenly write:
>
>         BSF PORTA,Relay    ;Turn on the relay
>         or
>         PORTA.Relay = 1;   // Turn on the relay.
>
>     You can eliminate this common source of errors by including the
>     port name in your #define:
>
>         #define Relay PORTB,0
>         or
>         #define Relay PORTB.0
>
>     then:
>
>         BSF Relay          ;Turn on the relay in assembly.
>         or
>         Relay = 1;         // Turn on the relay in C.

This works fine for addressing the individual port bit, but does not help
you if you need to access the whole register containing the bit, or need to
use the bit number other than with the port register.

A better way it to use my /INBIT and /OUTBIT preprocessor directives.  The
project include file would contain:

/outbit  relay    porta 0 0   ;relay on when 1, off when 0

This automatically causes a bunch of assembler constants to be defined.
Here are some example instructions that could be found in a module using the
include file.  These are just code snippets not meant to be useful code:

         dbankif  relay_reg   ;set banks for access to RELAY port reg
         bsf      relay_pin   ;turn on the relay
         .
         .
         bsf      shadow, relay_bit ;enable relay in the shadow copy
         .
         .
         dbankif  relay_tris
         bsf      relay_tris, relay_bit ;float the relay output pin

There is a lot more to the preprocessor.  All the details can be found at
http://www.embedinc.com/pic/.  You can follow the links to download your own
copy of all the PIC development tools.


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Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

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