dos33fsprogs/interlace_demo/rasterbars.s

; Uses the 40x48d page1/page2 every-1-scanline pageflip mode

; self modifying code to get some extra colors (pseudo 40x192 mode)

; by deater (Vince Weaver) <vince@deater.net>

; Zero Page
FRAMEBUFFER	= $00	; $00 - $0F
YPOS		= $10
YPOS_SIN	= $11
CH		= $24
CV		= $25
GBASL		= $26
GBASH		= $27
BASL		= $28
BASH		= $29
FRAME		= $60
BLARGH		= $69
DRAW_PAGE	= $EE
LASTKEY		= $F1
PADDLE_STATUS	= $F2
TEMP		= $FA
WHICH		= $FB

OUTL		= $FE
OUTH		= $FF


; Soft Switches
KEYPRESS= $C000
KEYRESET= $C010
SET_GR	= $C050 ; Enable graphics
FULLGR	= $C052	; Full screen, no text
PAGE0	= $C054 ; Page0
PAGE1	= $C055 ; Page1
LORES	= $C056	; Enable LORES graphics
PADDLE_BUTTON0 = $C061
PADDL0	= $C064
PTRIG	= $C070

; ROM routines

TEXT	= $FB36				;; Set text mode
HOME	= $FC58				;; Clear the text screen
WAIT	= $FCA8				;; delay 1/2(26+27A+5A^2) us


start_rasterbars:

	;===================
	; init screen
	jsr	TEXT
	jsr	HOME
	bit	KEYRESET

	;===================
	; init vars

	lda	#0
	sta	DRAW_PAGE
	sta	WHICH

	;=============================
	; Load graphic page0

	lda	#$0c
	sta	BASH
	lda	#$00
	sta	BASL                    ; load image to $c00

	lda	WHICH
	asl
	asl				; which*4
	tay

	lda	pictures,Y
	sta	GBASL
	lda	pictures+1,Y
	sta	GBASH
	jsr	load_rle_gr

	lda	#4
	sta	DRAW_PAGE

	jsr	gr_copy_to_current	; copy to page1

	; GR part
	bit	PAGE1
	bit	LORES							; 4
	bit	SET_GR							; 4
	bit	FULLGR							; 4

;	jsr	wait_until_keypressed


	;=============================
	; Load graphic page1

	lda	#$0c
	sta	BASH
	lda	#$00
	sta	BASL                    ; load image to $c00

	lda	WHICH
	asl
	asl				; which*4
	tay

	lda	pictures+2,Y
	sta	GBASL
	lda	pictures+3,Y
	sta	GBASH
	jsr	load_rle_gr

	lda	#0
	sta	DRAW_PAGE

	jsr	gr_copy_to_current

;	; GR part
	bit	PAGE0

;	jsr	wait_until_keypressed


	;==============================
	; setup graphics for vapor lock
	;==============================

	jsr	vapor_lock

	; vapor lock returns with us at beginning of hsync in line
	; 114 (7410 cycles), so with 5070 lines to go

	; GR part
	bit	LORES							; 4
	bit	SET_GR							; 4
	bit	FULLGR							; 4

	jsr	gr_copy_to_current			; 6+ 9292

	; 5070 + 4550 = 9620
	;		9292
	;		  12
	;		   6
	;		====
	;		 310

	; - 3 for jmp
	; 307

	; Try X=9 Y=6 cycles=307

	ldy	#6							; 2
loopA:	ldx	#9							; 2
loopB:	dex								; 2
	bne	loopB							; 2nt/3
	dey								; 2
	bne	loopA							; 2nt/3

	jmp	display_loop						; 3

.align  $100

	;================================================
	; Display Loop
	;================================================
	; each scan line 65 cycles
	;       1 cycle each byte (40cycles) + 25 for horizontal
	;       Total of 12480 cycles to draw screen
	; Vertical blank = 4550 cycles (70 scan lines)
	; Total of 17030 cycles to get back to where was

	; We want to alternate between page1 and page2 every 65 cycles
        ;       vblank = 4550 cycles to do scrolling


display_loop:

.include "rasterbars_screen.s"

	;======================================================
	; We have 4550 cycles in the vblank, use them wisely
	;======================================================

	; 4550	-- VBLANK
	; -162	-- erase     22+8+6+126 = 162
	; -174  -- raster 16+26+6+126 = 174
	;  -10  -- keypress
	;=======
	; 4204

pad_time:

	; we erase, then draw
	; doing a blanket erase of all 128 lines would cost 3459 cycles!

	; erase red

	lda	#$00				; 2
	sta	smc_raster_color1_1+1		; 4
	sta	smc_raster_color1_2+1		; 4
	sta	smc_raster_color2_1+1		; 4
	sta	smc_raster_color2_2+1		; 4
	sta	smc_raster_color3_1+1		; 4
					;=============
					;	22

	lda	red_x				; 4
	and	#$7f				; 2
	tax					; 2

	jsr	draw_rasterbar			; 6+126


	; move red

	ldy	red_x				; 4
	lda	movement_table,Y		; 4
	sta	red_x				; 4
	and	#$7f				; 2
	tax					; 2
					;==========
					;	 16

	; draw red

	lda	#$33				; 2
	sta	smc_raster_color1_1+1		; 4
	sta	smc_raster_color1_2+1		; 4
	lda	#$bb				; 2
	sta	smc_raster_color2_1+1		; 4
	sta	smc_raster_color2_2+1		; 4
	lda	#$ff				; 2
	sta	smc_raster_color3_1+1		; 4
					;=============
					;	26


	jsr	draw_rasterbar			; 6+126

	; Try X=43 Y=19 cycles=4200 R4

	nop
	nop

	ldy	#19							; 2
loop1:	ldx	#43							; 2
loop2:	dex								; 2
	bne	loop2							; 2nt/3
	dey								; 2
	bne	loop1							; 2nt/3


	lda	KEYPRESS				; 4
	bpl	no_keypress				; 3
	jmp	display_loop
no_keypress:

	jmp	display_loop				; 3


	;========================
	; Draw a rasterbar
	;	unroll as memory is free!  haha
	;========================
	; X is location

	; 2+22+24+24+24+24+6 = 126

draw_rasterbar:

	ldy	#0			; 2
					;====

	lda	y_lookup_l,X		; 4
	sta	OUTL			; 3
	lda	y_lookup_h,X		; 4
	sta	OUTH			; 3

smc_raster_color1_1:
	lda	#$33			; 2
	sta	(OUTL),Y		; 6
				;============
				;	22

	inx				; 2
	lda	y_lookup_l,X		; 4
	sta	OUTL			; 3
	lda	y_lookup_h,X		; 4
	sta	OUTH			; 3

smc_raster_color2_1:
	lda	#$bb			; 2
	sta	(OUTL),Y		; 6

	inx				; 2
	lda	y_lookup_l,X		; 4
	sta	OUTL			; 3
	lda	y_lookup_h,X		; 4
	sta	OUTH			; 3

smc_raster_color3_1:
	lda	#$ff			; 2
	sta	(OUTL),Y		; 6

	inx
	lda	y_lookup_l,X		; 4
	sta	OUTL			; 3
	lda	y_lookup_h,X		; 4
	sta	OUTH			; 3

smc_raster_color2_2:
	lda	#$bb			; 2
	sta	(OUTL),Y		; 6

	inx
	lda	y_lookup_l,X		; 4
	sta	OUTL			; 3
	lda	y_lookup_h,X		; 4
	sta	OUTH			; 3

smc_raster_color1_2:
	lda	#$33			; 2
	sta	(OUTL),Y		; 6

	rts				; 6








	;==================================
	; HLINE
	;==================================

	; Color in A
	; Y has which line
hline:
	pha							; 3
	ldx	gr_offsets,y					; 4+
	stx	hline_loop+1					; 4
	lda	gr_offsets+1,y					; 4+
	clc							; 2
	adc	DRAW_PAGE					; 3
	sta	hline_loop+2					; 4
	pla							; 4
	ldx	#39						; 2
hline_loop:
	sta	$5d0,X		; 38				; 5
	dex							; 2
	bpl	hline_loop					; 2nt/3
	rts							; 6

	;==========================
	; Clear gr screen
	;==========================
	; Color in A
clear_gr:
	ldy	#46
clear_page_loop:
	jsr	hline
	dey
	dey
	bpl	clear_page_loop
	rts

gr_offsets:
	.word	$400,$480,$500,$580,$600,$680,$700,$780
	.word	$428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8
	.word	$450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0


.include "../asm_routines/gr_unrle.s"
.include "../asm_routines/keypress.s"
.align $100
.include "rasterbars_table.s"
.include "movement_table.s"
.include "gr_copy.s"
.include "vapor_lock.s"
.include "delay_a.s"

pictures:
	.word rb_bg_low,rb_bg_high

.include "rb_bg.inc"

red_x:	.byte $10