Re: A92: 256K & interrupt routines


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Re: A92: 256K & interrupt routines



Even if you use the higest wrap-around, someone might eventually find a 
way to have 1MB of internal ROM.  You should say in the FAQ that this is 
a possibility, and that programmers should realize this.  Other than 
that, use the technique.



Chris Lambert
clambert@geneva.edu
calan@hotmail.com
URL: www.geocities.com/siliconvalley/peaks/6869

On Fri, 24 Oct 1997, Bryan Christopher Turner wrote:

> On Oct 23,  3:49pm, Jean-Jacques MICHEL wrote:
> > Subject: RE: A92: 256K & interrupt routines
> > >>> Could somebody justify the use of :
> > >>>
> > >>>         move.w  #$2700,sr
> > >>>         move.l  ($020064),old_int_1
> > >>>         move.l  #int_1,($020064)
> > >>>         move.w  #$2000,sr
> >
> > >>It saved you the trouble of setting/clearing the bit that
> > >>enables/disabled the "unauthorized writing under $120" trap.
> > >>It's the same technique used by Fargo itself - the memory wraps around
> > >>at $020000, and the trap isn't activated "up there".
> >
> > That's pretty obvious, why didn't I thought about it sooner ?
> > Thank you for your answer.
> >
> > May I suggest then to use $040064 instead...
> > (I tested SPRITE.ASM with this and it worked fine with my 256K Fargo v1.7
>  :-)
> 
>    This was discussed way back when, and yet I think only two programs have
> supported this feature.  I would like to get this little tidbit added to the
> programming FAQs.  In fact, we should use the highest possible address instead
> of the 'next' wrap around.  I believe this would be $0E0064.
> 
> --Bryan
> bcturner@eos.ncsu.edu
> 


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