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Atari coding BBS
| Re: Vector Routines |
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Posted by: evil
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May,05.2013-12:08
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I'm probably too dumb to understand what you want.
But it sounds like you need code to run on an interrupt that breaks the mainloop while doing it.
There are then several options;
1. VBL - this will be a 50 Hz PAL (once per frame) interrupt
2. HBL - this will be a 15650 Hz (once per scanline) interrupt
3. MFP - four programmable interupts (Timer A, B, C and D)
Example to steal the VBL vector, assuming you are in supervisor mode.
;setup
move.w #$2700,sr
move.l $70.w,save_old_vbl
move.l #my_vbl,$70.w
move.w #$2300,sr
;restore
move.w #$2700,sr
move.l save_old_vbl,$70.w
move.w #$2300,sr
vbl: rte
save_old_vbl: ds.l 1
Remember that the VBL-code need to store/restore the cpu-registers you use there.
--
Anders Eriksson
ae@dhs.nu
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