Re: A83: Switching the calculator off
[Prev][Next][Index][Thread]
Re: A83: Switching the calculator off
I thought my tutorials covered this quite well :)...obviously not.
James.
----------
> From: Conway <conway@ssc.net.au>
> To: assembly-83@lists.ticalc.org
> Subject: Re: A83: Switching the calculator off
> Date: Tuesday, May 05, 1998 5:06 AM
>
>
> Thank you so much for that info Trey. I did read that somewhere, but
didn't
> fully understand it. Now I think I do. Now let me see if this is right.
> "Push" saves the regester into memory (or stack as it really called), and
> pop loads it back into the register. Question, say you do this...
> ld hl, 1234h
> ld bc, 5678h
> push hl
> push bc
> pop hl ; ****** My question is in this case, is the
number
> poped into hl, is that
> 5678h or is it 1234h? My guess
that
> it is 5678h. Am I right or
> completly wrong?
> Thank you
> From Conway
>
> -----Original Message-----
> From: Trey Jazz <joemama@minot.com>
> To: assembly-83@lists.ticalc.org <assembly-83@lists.ticalc.org>
> Date: Monday, 4 May 1998 3:49
> Subject: Re: A83: Switching the calculator off
>
>
> >
> >>I didn't use any push or pop's (mainly cause I don't understand them).
> >
> >o ok.... pushes and pops are a big way to save lots of memory in
routines
> >and a good way to keep from doing stupid stuff.
> >push af ; this pushes af onto the stack
> >pop af ;this pops the last values put on the stack into af
> >this can be done with af,bc,de,hl theres also calls to push and pop the
OPs
> >
> >heres one use for the push/pop
> > ld hl,sprite
> > ld b,14
> > ld a,0 ;load the x-coord of the sprite into a
> >loop:
> > ld e,y-coord
> > push af ;push whatever is in af onto the stack because the call
destroys a
> > push bc ;push this too because b and c are destroyed too
> > call PutSprite
> > pop bc ;pop the last register you pushed first so you dont end up with
the
> >values in the wrong registers
> > pop af ;pop the values back into a
> > push bc ;push the original loop counter so we dont lose it
> > ld b,8
> >loop2:
> > inc a ;increases a 8 times so the next sprite is side by side with the
> last
> >one
> > djnz loop2
> > pop bc ;restore the original loop counter
> > djnz loop
> >
>