include "base_irq3.s"

********* CONST ***********************************

W = 320				; screen/bitplane width in memory (in px)
H = 256				; screen/bitplane height in memoty (in px)
BPLS = 2			; number of bitplanes
LEFF = 320			; effective screen width (DDFSTOP-DDFSTRT)*2+16
MODULOS = W/8*BPLS-LEFF/8	; number of bytes to skip per line
				; W/8-LEFF/8 if non IL
				; W/8*BPLS-LEFF/8 if IL
BPLSIZE = W/8			; bytes taken by one bitplane
				; W/8*H if non IL ; W/8 if IL
LINESIZE = W/8*BPLS		; Lentght of image line in bytes
				; W/8 if non IL   ; W/8*BPLS if IL

********* INIT ************************************

run:
	lea CUSTOM,a6			; move the base to a6
	move.w #$8380,DMACON(a6)	; activate copper+ BPL in DMA channel

	move.l #copper,COP1LCH(a6)	; move new copper to copper register
	move.w #0,COPJMP1(a6)		; (H and L) & activate new copper

	lea copperbpl,a0		; set the needed variables before
	move.l #screen,d0		; branching to rotine to 
	bsr pokebpls			; poke bpls memoory ptr to copper

;	move.w #$FFFF,screen		; test line

	
	lea irq3,a0			; replace irq3 with our own 
	move.l a0,$6C.w			; interrupt routine that will be
					; played each time the vetrical 
					; blank occurs
	move.w #$C020,INTENA(a6)	; allow VBL interrupts!

********* MAIN ************************************

main:
	bsr waitVBI		; wait for the vertical blanc
				; before updating the screen
	
	btst #6,$BFE001		; is lmb prssed
	bne main		; 0 = pressed

	rts


********* IRQ3 ************************************

irq3:
	movem.l	a0-a6/d0-d7,-(sp)	; save on stack

	lea	CUSTOM,a6		; just to be sure
	move.w	INTREQR(a6),d0		; what did trigger the irq
	and.w	#$0070,d0		; mask VBI COP BLT interrupts
					; and then acknowledge only
					; the one that was triggered
	move.w	d0,INTREQ(a6)		; is necessary to tell the system that
	move.w	d0,INTREQ(a6)		; the interrupt is beign handeld
	move.w	d0,INTREQ(a6)		; need to be 3 time, dur to a bug
					; fro cpu > 68000
					; https://amycoders.org/tutorials/frametime.html
	add.w	#1,col
	move.w col,$DFF180
	
	; do stuff
	
	movem.l	(sp)+,a0-a6/d0-d7	; retore state from stack
	rte				; retun with rtE not rtS!


********* ROUTINES ***********************************

*** poke bipls addresses into copper
*   a0: bpls pointer in copperlist
*   d0: address of bpls in memory
pokebpls:
	movem.l d0/d7/a0,-(sp)		; save used registers on the stack

	moveq #BPLS-1,d7		; loop counter = number of bpls
loopbpl:
	move.w d0,6(a0)			; low word in BPL1PTL
	swap d0				; swap low and high
	move.w d0,2(a0)			; high word into BPL1PTH
	swap d0				; original address back
	add.l #BPLSIZE,d0		; d0 points to bpl2 data
	add.l #8,a0			; a0 points to next bplptr
	dbf d7,loopbpl

	movem.l (sp)+,d0/d7/a0		; restore saved registers
	rts

********* DATA in FAST MEM ************************

col:
	dc.w 0

********* DATA in CHIP MEM ************************

	section copperlist,data_C
copper:
	dc.w BPLCON0,BPLS<<12!$0200 ; set bitplane number

	dc.w DIWSTRT,$2C81	; define display window size
	dc.w DIWSTOP,$F4C1	; 320 X 200 pixels
				; $F4C1 for 200 px high
				; $2CC1 dor 256 px high
	dc.w DDFSTRT,$38	; define display data fetch
	dc.w DDFSTOP,$D0	; size to 320 pxels

	dc.w BPL1MOD,MODULOS	; skip xxx px per line
	dc.w BPL2MOD,MODULOS 

copperbpl:
	dc.w BPL1PTH,$0000	; give denise the pointer
	dc.w BPL1PTL,$0000	; to the first bitplane
	dc.w BPL2PTH,$0000	; give denise the pointer
	dc.w BPL2PTL,$0000	; to the second bitplane
	dc.w BPL3PTH,$0000	; give denise the pointer
	dc.w BPL3PTL,$0000	; to the third bitplane
	dc.w BPL4PTH,$0000	; give denise the pointer
	dc.w BPL4PTL,$0000	; to the fotrh bitplane
	dc.w BPL5PTH,$0000	; give denise the pointer
	dc.w BPL5PTL,$0000	; to the fifth bitplane
	dc.w BPL6PTH,$0000	; give denise the pointer
	dc.w BPL6PTL,$0000	; to the sixth bitplane

palette:
	dc.w $0180,$0000
	dc.w $0182,$0FFF
	dc.w $0184,$0F00
	dc.w $0186,$000F


	dc.w $FFFF,$FFFE	; copper end

screen:
	dcb.b W/8*H*BPLS,0	; reserve the memory fir the given parameters 
				; and set them to color 0