True that the bios could change, however, I have dumped the bios from all
of the current GBA systems, GBA, GBA-SP, and GB-Player, and they are all
100% identical, so it is unlikely they will change the bios until they come
out with the next gameboy system.

But as Stephen said, if you desire to get into an interrupt, use a timer
to do that.
----- Original Message -----
From: "Stephen Stair" <sgstair@...>
To: <gbadev@yahoogroups.com>
Sent: Friday, February 27, 2004 5:14 PM
Subject: Re: [gbadev] swi calls


> Yeah, SWI's are locked in the GBA's bios.
>
> if you were desperate to make an interrupt, you could use one of the timer
> interrupts, and set it up so the timer would overflow on the next cycle or
> somesuch... But there's not much reason to use interrupts for stuff like
> that because all interrupts have a fairly significant overhead (>50
cycles),
> so you might as well just call some function to do the work for you.
>
> Additionally, you *could* attempt to find a SWI vector that would do
> something favorable (the SWIs are not bound-checked, so there *may* be
some
> 4-byte address somwhere in the data/code after the jumptable that would
jump
> to some place in iwram, or something similar that could be useful...)
> But, that's bios-dependent, if they changed the bios your code would no
> longer work... not a recommended practice :)
>
> -Stephen
> ----- Original Message -----
> From: "Michael Reid - CSCI/P2003" <m6reid@...>
> To: <gbadev@yahoogroups.com>
> Sent: Friday, February 27, 2004 4:54 PM
> Subject: [gbadev] swi calls
>
>
> > hi,
> >
> > i'll start with the obligatory, "i'm new to this" bit. i've only been
> > playing around w/ programming the gba for about a month.
> >
> > anyhow, i would like to be able to add my own system calls, via the swi
> > instruction, however, the little info i have found about this implies
that
> > the system calls are BIOS only, and that there is no way to add any
> > user-defined calls.
> >
> > does anyone know if this is true or not? has anyone been able to define
> > their own syscalls?
> >
> > if not, then can anoyone think of a way to force a hardware interrupt
> > (enter irq mode)?
> >
> > thanks
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>