Andrew Warren wrote:
>    Yeah, but isn't #DEFINE a significantly better way to do that?

Maybe specifically for flags, but I think Bob has a valid point in that
CBLOCK is useful for creating an enumerated list of values.

>    If you do it with CBLOCK-assigned bit names, you must remember which
>    register holds each flag (I assume that the awkward "FLAG_" prefix
>    is there to aid your memory), but if you do it with #DEFINEs, you
>    don't have to remember anything:
>
>        #DEFINE HAPPY  FLAGS,0
>        #DEFINE DOPEY  FLAGS,1
>        #DEFINE DOC    FLAGS,2
>        #DEFINE SLEEPY FLAGS,3

This makes accessing the flag with something like a BCF/BSF instruction
easy, but what happens when you have more than 8 flags and you want to
access the byte containing the flags in your code directly, or you need to
know its bank?

>
>            BSF   HAPPY
>            BCF   DOPEY
>            BTFSS DOC
>            BCF   SLEEPY
>
>    Hmm... I guess you could combine the two... Put all your flags in a
>    big CBLOCK list, then do:
>
>        #DEFINE HAPPY  FLAGS,FLAG_Happy
>        #DEFINE DOPEY  FLAGS,FLAG_Dopey
>        #DEFINE DOC    FLAGS,FLAG_Doc
>        #DEFINE SLEEPY FLAGS,FLAG_Sleepy
>
>    It's hard to imagine a scenario in which that would be less trouble
>    than it was worth, though.

That's why I created the /FLAG directive in my preprocessor.  You write one
line of code like:

  /FLAG  happy

and it automatically allocates the next bit in registers names GFL0 - GFLn
and defines several symbols:

  flag_happy  -  String substition for use with BCF/BSF as above

  flag_happy_regn  -  0-N number of the GFLn variable containing flag

  flag_happy_reg  -  Address of the GFLn variable containing flag

  flag_happy_bit  -  0-7 bit number within GFLn variable

The preprocessor is part of my PIC development environment available for
free at http://www.embedinc.com/pic.  You can click on the PREPIC link to
see the documentation file for more details on the /FLAG directive and all
the other things the preprocessor can do.


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