Section	Skel1,Code

	Opt	C-,O+,w-

	; Writtem by Shagratt/LSD
	
	; this system takeover is 680x0 compatable
	; and gives you lots of processor time

Start:	lea	$dff000,a5		; hardware base address

	Move.w	$1c(a5),OldInt	; Save Old Interupts
	Move.w	$02(a5),OldDma	; Save Old DMA

	Move.w	#$7fff,$9a(a5)	; Clear DMA
	Move.w	#$7fff,$96(a5)	; Clear Interupts
	Move.w	#$7fff,$9c(a5)	; Clear Interupt Requests
	
	bsr	GetVBR		; needed on 680x0
	
	Move.b	#$7f,$bfed01	; kill timers
	Move.l	$6c(a4),OldV3	; save level 3 int

	Move.l	#my_level3,$6c(a4)	; put new copper interupt
	Move.l	#my_copper,$80(a5) 	; Address of copper 1
	Move.w	#$c010,$9a(a5)	; Start interupts

	Move.w	#$83ef,$96(a5)	; Start DMA
	Move.w	#1,$88(a5)		; Strobe for copper start

	move.l	#scr,d0
	move.w	d0,bitplane0_lo
	swap	d0
	move.w	d0,bitplane0_hi

	move.l	#sprite,d0		; clear all sprites
	lea	spr0_ptrs,a0
	move.w	#7,d1
.loop	move.w	d0,6(a0)
	swap	d0
	move.w	d0,2(a0)
	swap	d0
	lea	8(a0),a0
	dbf	d1,.loop

wait:	move.w	$dff006,$dff180
	btst	#6,$bfe001
	bne.s	wait		; wait for lmb

	; this bit from here on wouldn't normaly get executed

	bsr	GetVBR		; needed on 680x0
	Move.l	OldV3,$6c(a4)	; restore old l3

	lea	$dff000,a5		; hardware base address
		
	move.l	4,a6
	Lea	GfxLib,a1		; Pointer to Library Text
	jsr	-132(a6)		; forbid
	Move.l	4.w,a6		; Exec
	Moveq.l	#0,d0		; Clear D0
	Jsr	-$228(a6)		; Open Library
	
	Move.l	d0,a1			
	Move.l	$26(a1),$80(a5)	; restore copper 1
	Move.l	$32(a1),$84(a5)	; restore copper 2

	Move.w	OldInt,d0		; start old interupts
	Or.w	#$8000,d0
	Move.w	d0,$9a(a5)
	Move.w	OldDma,d0		; start old DMA
	Or.w	#$8000,d0
	Move.w	d0,$96(a5)
	Move.b	#$9b,$bfed01	; Start Timers
	Move.l	4.w,a6		; Close Gfx lib
	Jsr	-$19e(a6)
	move.l	4.w,a6
	jsr	-138(a6)		; permit

	move.w	#0,$bfec00		; clear kbd

	Moveq.l	#0,d0		; No errors
	Rts			; Exit

	*--------------------------------------------------*	

GetVBR	Move.l	4.w,A6
	Moveq	#15,D7
	And	296(A6),D7		;check processor
	Beq	.68000
	Lea	.Find(Pc),A5
	Jsr	-30(A6)		; supervisor
.68000	Move.l	D7,a4
	Rts

.Find	dc.l	$4e7a7801		;Movec.l	VBR,D7
	Rte

	*--------------------------------------------------*	

my_level3:	Movem.l	d0-d7/a0-a6,-(a7)	
	Move.w	#$10,$dff09c	; Serviced Interupt

Exit:	Movem.l	(a7)+,d0-d7/a0-a6
	Rte			; Return from Interupt

	*--------------------------------------------------*	

oldint:		dc.l	0
olddma:		dc.l	0
oldv3:		dc.l	0
gfxlib:		dc.b	"graphics.library",0
		even

	Section	Skel2,data_C

my_copper:		dc.w	$100,$1200	; 4 bp - lo res
		dc.w	$104,$a	; bp control reg
		dc.w	$108,0	; bp modulo - odd
		dc.w	$10a,0	; bp modulo - even
		dc.w	$180,0	; colour 0 to black
		dc.w	$102,0
		
		dc.w	$08e,$2c81	; bp window start left
		dc.w	$090,$2cc1	; bp window bot right
		dc.w	$094,$d0	; bp stop horz
		dc.w	$92,$38

spr0_ptrs:		dc.w	$120,0,$122,0
		dc.w	$124,0,$126,0
		dc.w	$128,0,$12a,0
		dc.w	$12c,0,$12e,0
		dc.w	$130,0,$132,0
		dc.w	$134,0,$136,0
		dc.w	$138,0,$13a,0
		dc.w	$13c,0,$13e,0
		
		dc.w	  $e0
bitplane0_hi:	dc.w	0,$e2
bitplane0_lo:	dc.w	0
		
cmap:		dc.w	$180,$000
		dc.w	$182,$fff

		dc.w	$1a0,$000
		dc.w	$1a2,$eee
		dc.w	$1a4,$aaa
		dc.w	$1a6,$666
				
		dc.w	$ffe1,$fffe	; end of ntsc screen
		dc.w	$3001,$ff00	; end of pal screen
		dc.w	$9c,$8010	; irq set bits - restart copper
		dc.w	$ffff,$fffe	; end of copper list

sprite:		dc.l	0,0
		
scr:		ds.l	10*256

	end