On Mon, 13 Jul 1998, Brian Gracia wrote:
-snip-
>
> Where I am lacking is in the fact that while I can program in several
> computer languages, pic code is just not the same!!!  Can someone help me
> by translating some simple program building blocks like IF..Then, Do
> While..Loop, For I.., etc into pic code.  I need to see these in order to
> get a basic footing, and then I can begin to understand.  Doing this is
> like showing someone how to read a tape measure.  Pretty soon, with a set
> of plans (psudo code), and the basic building blocks, they can build a
> house.  Well almost, but you get my drift.

Since you already know a few other languages, analyze how you picked
the(m) up. Do you learn best by yourself, in class, from an organized
course, or are you the kind that rips things apart to learn what's inside
? Then, pick a learning method that suits you best.

A book is a good start, if you are that kind of guy. If you learn by
yourself, simply learn the instruction set by heart and start doing some
simple applications (peek at the application notes from Microchip in the
process). If you like to program using templates, get a book. The author
usually uses his own programming style throughout, and that is as good
a 'template' as any.

Translating structured programming constructs into PIC assembly is not so
direct as you might think it is.

For example for an IF...THEN...ELSE you would have to work out an
expression for the IF part that sets a bit or a register and write code
like this:

        ; IF
        ; code for if-expression here

        ; final comparison: ZF of the PSW is not set IF true (C convention)
        btfsc   PSW, ZF
        goto    if_false

        ; THEN
        ; code for true case here

        goto    if_end

        ; ELSE
if_false:
        ; code for false case here

if_end:
        ; FI

Notice that there is no boilerplate code, only the structure of the code
is essential. You have to find a solution for every case as you go, there
is no real constraint in a symmetrical-register architecture machine as
the PIC is.

DO..WHILE etc translate much in the same way. You keep the general
structure of the construct, but you implement it with the mnemonics that
get you to your goal. Putting labels with structured construct part names
in them into the source will help you understand the code later.

Notice that remarkably few advanced assembly programmers bother about
structured code construction on PICs ;) Hack mode is much more natural <G>

hope this helps,

        Peter