Slightly simplified the blit routine

009.anim_blit/anim_blit.s

@@ -7,21 +7,20 @@
 entry:
 	lea 	CUSTOM,a6
 	bsr	init
-	
+
 	lea	bitplanes(pc),a0
 	lea	emoji,a1
 	lea	emojiMask,a2
 .mainLoop:
+	bsr 	waitvbl
+	bsr	moveBlitterObject
 	bra.s	.mainLoop
 
 	include	"blit.s"
 	include "init.s"
-
-level3InterruptHandler:
-	movem.l	d0-a6,-(sp)	
-	move.w	#INTF_VERTB,INTREQ(a6)	; clear interrupt bit	
-
-.moveBlitterObject:	
+	include "utils.s"
+	
+moveBlitterObject:	
 	lea	xpos(pc),a3
 	lea	ypos(pc),a4
 	add.l	#1,xpos		; move the blitter object one pixel to the left
@@ -35,12 +34,13 @@ level3InterruptHandler:
 	bne.s	.done
 	move.l	#0,ypos					; wrap y back to 0
 .done:
+	rts
 
-		
-.interruptComplete:
-	movem.l	(sp)+,d0-a6
-	rte
-
+	
+installPalette:
+	include "out/image-palette.s"
+	rts
+	
 xpos:	dc.l	0
 ypos:	dc.l	0
 	

009.anim_blit/blit.s

@@ -51,20 +51,16 @@ blitObject64:
 	;; d1 = YPOS
 	;; d4 = XPOS_BYTES
 
-	move.l	d0,d2	; d2 = XPOS
-	move.l	d0,d3	; d3 = XPOS
-	lsr.l	#3,d3	; d3 = XPOS_BYTES
-	move.l	d3,d4	; d4 = XPOS_BYTES
-	move.l	d0,d3	; d3 = XPOS
-	lsr.l	#4,d3	; d3 = XPOS_WORDS
-	lsl.l	#4,d3	; d3 = XPOS_NEAREST_WORD
-	sub.l	d3,d2	; d2 = num pixels to shift
-	lsl.w	#8,d2	; BLIT_SOURCE_SHIFT<<BLIT_ASHIFTSHIFT
-	lsl.w	#4,d2 	; BLIT_SOURCE_SHIFT<<BLIT_ASHIFTSHIFT
+ 	move.w	d0,d4	; d4 = XPOS
+	lsr.w	#3,d4	; d4 = XPOS_BYTES
 
-	move.w	d2,BLTCON1(A6)
-	ori.w   #BLIT_SRCA|BLIT_SRCB|BLIT_SRCC|BLIT_DEST|BLIT_LF_MINTERM,d2
-	move.w	d2,BLTCON0(A6)
+	;; this shift will give us the bits to shift (bits 0-3) in bits (12-15) of d0
+	lsl.w	#8,d0	; BLIT_SOURCE_SHIFT<<BLIT_ASHIFTSHIFT
+	lsl.w	#4,d0 	; BLIT_SOURCE_SHIFT<<BLIT_ASHIFTSHIFT
+
+	move.w	d0,BLTCON1(A6)
+	ori.w   #BLIT_SRCA|BLIT_SRCB|BLIT_SRCC|BLIT_DEST|BLIT_LF_MINTERM,d0
+	move.w	d0,BLTCON0(A6)
 	
 	move.w	#$ffff,BLTAFWM(a6)	; no mask for first word
 	move.w	#$0000,BLTALWM(a6) 	; mask out last word
@@ -75,13 +71,13 @@ blitObject64:
 	move.l 	a2,BLTAPTH(a6)	; mask bitplane
 	move.l 	a1,BLTBPTH(a6)	; bob bitplane
 
-	move.l	#SCREEN_WIDTH_BYTES*SCREEN_BIT_DEPTH,d3	; d3 = SCREEN_WIDTH_BYTES*SCREEN_BIT_DEPTH
+	move.w	#SCREEN_WIDTH_BYTES*SCREEN_BIT_DEPTH,d3	; d3 = SCREEN_WIDTH_BYTES*SCREEN_BIT_DEPTH
 	mulu.w	d1,d3					; d3 = YPOS*SCREEN_WIDTH_BYTES*SCREEN_BIT_DEPTH
-	move.l 	a0,d2					; d2 = #bitplanes
-	add.l 	d4,d2					; d2 = #bitplanes+XPOS_BYTES
-	add.l	d3,d2					; d2 = #bitplanes+XPOS_BYTES+(YPOS*SCREEN_WIDTH_BYTES*SCREEN_BIT_DEPTH)
-	move.l 	d2,BLTCPTH(a6) ;background top left corner
-	move.l 	d2,BLTDPTH(a6) ;destination top left corner
+	move.l 	a0,d0					; d0 = #bitplanes
+	add.w 	d4,d0					; d0 = #bitplanes+XPOS_BYTES
+	add.w	d3,d0					; d0 = #bitplanes+XPOS_BYTES+(YPOS*SCREEN_WIDTH_BYTES*SCREEN_BIT_DEPTH)
+	move.l 	d0,BLTCPTH(a6) ;background top left corner
+	move.l 	d0,BLTDPTH(a6) ;destination top left corner
 
 	move.w 	#(BLIT_BOB_HEIGHT64*SCREEN_BIT_DEPTH)<<6|(BLIT_BOB_WIDTH64_WORDS),BLTSIZE(a6)	;rectangle size, starts blit
 	movem.l (sp)+,d0-a6

009.anim_blit/init.s

@@ -2,12 +2,10 @@
 init:
 	movem.l	d0-a6,-(sp)
 	move	#$7ff,DMACON(a6)	; disable all dma
+	move	#$7fff,INTENA(a6) ; disable all interrupts	
 
-	lea	level3InterruptHandler(pc),a3
-	move.l	a3,LVL3_INT_VECTOR
-	move	#$7fff,INTENA(a6) ; disable all interrupts
-
-	include "out/image-palette.s"
+	;; set up default palette
+	bsr.s	installPalette
 	
 	;; set up playfield
 	move.w  #(RASTER_Y_START<<8)|RASTER_X_START,DIWSTRT(a6)
@@ -38,6 +36,6 @@ init:
 	move.l	a0,COP1LC(a6)
  	move.w  COPJMP1(a6),d0
 	move.w	#(DMAF_BLITTER|DMAF_SETCLR!DMAF_COPPER!DMAF_RASTER!DMAF_MASTER),DMACON(a6)
-	move.w	#(INTF_SETCLR|INTF_VERTB|INTF_INTEN),INTENA(a6)
+	;; move.w	#(INTF_SETCLR|INTF_VERTB|INTF_INTEN),INTENA(a6)
 	movem.l (sp)+,d0-a6
 	rts

009.anim_blit/utils.s

@@ -7,3 +7,17 @@ waitvbl:
 	movem.l (sp)+,d0-a6
 	rts	
 
+
+
+waitRaster:		;wait for rasterline d0.w. Modifies d0-d2/a0.
+	movem.l d0-a6,-(sp)
+	move.l #$1ff00,d2
+	lsl.l #8,d0
+	and.l d2,d0
+	lea $dff004,a0
+.wr:	move.l (a0),d1
+	and.l d2,d1
+	cmp.l d1,d0
+	bne.s .wr
+	movem.l (sp)+,d0-a6
+	rts