Stephen D. Barnes <stephendbarnes@cox.net> wrote:
> Olin Lathrop Wrote:
> > bss     myvar, 2, 2         ;define 16 bit variable
> >         mov     #myvar, w0  ;point W0 to start of MYVAR
> >         mov.b   [w0++], w1  ;get low byte of MYVAR into W1
> >         mov.b   [w0], w2    ;get high byte of MYVAR into W2
> 
> I just want to be sure I really understand what happens here...please 
> correct me if I am wrong.
> 
> 
> .bss    myvar, 2, 2           ;defines variable, 2 bytes long, aligned
>         mov    #myvar, w0     ;move the contents of myvar to w0     
>         mov.b  [w0++], w1     ;move 1 byte of w0 to w1(low byte) and
>                               ; post increment the the "effective address"
>                               ; which means the w0 low byte will now
>                               ; contain what was the high byte before the
>                               ; increment? 

Not quite.

        ; This instruction places an immediate value that is the
        ; *address* of myvar into w0. In Olin's terminology, w0 is now
        ; a "pointer" to myvar where it resides in memory.
        mov    #myvar, w0

        ; This instruction uses w0 as an address, moves the memory byte at
        ; that address (the low byte of myvar) into w1, then increments w0
        ; so that it contains the address of ("points to") the high byte
        ; of myvar.
        mov.b  [w0++], w1

        ; This instruction use w0 as an address again, moves the byte there
        ; (the high byte of myvar) into w2. No increment of w0 this time.
        mov.b   [w0], w2

-- Dave Tweed
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist