G'day piclisters

I have just discovered a couple of simple macros that I'd like comments on.
But first the problem.

I use #define to define my port pins because I don't want to have to
remember which port they belong to (plus it is easier!).

example:
    #define SDATA   RB,5

This is well and good.  The problem arises when I want to manipulate a bit
mask based on that pin.  The wonderful expression someone came up with:

    iorlw       b'00000001' << pin

requires the form of port,pin to work.  So, for all these years, I've been
mixing the two styles in my code and avoiding port pin bit masks whenever
possible.

It finally occured to me today that a #define statement already has the
information needed to make a bit mask.  All it takes is a couple of one line
macros as follow:

sethi           MACRO   port,pin
    iorlw       b'00000001' << pin
    endm

setlo           MACRO   port,pin
    andlw       ~ (b'00000001' << pin)
    endm

Usage is simple:  way up near the front of my source:

    #define     POT     GPIO,5
    (rest of pin definitions)
    DDR         EQU     b'00110000'     ;default port pin DDR

down somewhere in the code:
;generate bit mask for RC timer pin
    movlw       DDR             ;set pin to o/p
    setlo       POT
    tris        GPIO
        .
        .
        .
    movlw       DDR             ;set pin back to input
    sethi       POT
    trisi       GPIO

The nice thing about this is that it doesn't matter what the DDR constant
gets changed to - I explicitly set the tris bit for that pin.

Comments anyone?  I'm not particularily happy with my chosen macro names
(sethi and setlo) but thats what I came up with off the top of my head.
I've tested this with the DOS version 1.40 of MPASM - it generated the same
opcodes as explicit andlw and iorlw statements.

dwayne


Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, Alberta, CANADA
(403) 489-3199 voice     (403) 487-6397 fax