mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-06-10 13:29:57 +00:00
224 lines
2.5 KiB
ArmAsm
224 lines
2.5 KiB
ArmAsm
; Parallax HGR
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; by deater (Vince Weaver) <vince@deater.net>
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; Zero Page
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GBASL = $26
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GBASH = $27
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H2 = $2C
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COLOR = $30
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HGR_X = $E0
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HGR_Y = $E2
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HGR_COLOR = $E4
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HGR_HORIZ = $E5
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HGR_PAGE = $E6
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FRAME = $F0
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FRAME2 = $F1
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FRAME4 = $F2
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X2 = $FB
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COLORS = $FC
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; Soft Switches
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PAGE1 = $C054 ; Page1
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PAGE2 = $C055 ; Page2
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; ROM routines
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HGR = $F3E2
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HGR2 = $F3D8
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HCLR = $F3F2
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HPLOT0 = $F457 ;; plot at (Y,X), (A)
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WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
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HPOSN = $F411 ; (Y,X),(A) (values stores in HGRX,XH,Y)
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hgr_lookup_h = $1000
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hgr_lookup_l = $1100
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parallax:
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;===================
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; init screen
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jsr HGR2
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;===================
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; int tables
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ldx #191
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init_loop:
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txa
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pha
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jsr HPOSN
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pla
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tax
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lda GBASL
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sta hgr_lookup_l,X
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lda GBASH
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sec
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sbc #$40
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sta hgr_lookup_h,X
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dex
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cpx #$ff
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bne init_loop
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tax
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parallax_forever:
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inc FRAME ; 2
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lda FRAME
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lsr
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sta FRAME2
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lsr
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sta FRAME4
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;========================
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; update color
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lda FRAME
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; flip page
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lda HGR_PAGE ; $40 or $20
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pha
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asl
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asl
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rol
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tay
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lda PAGE1,Y
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pla
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eor #$60 ; flip draw_page
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sta HGR_PAGE
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ldx #191 ; init Y
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yloop:
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;==============
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; point GBASL/GBSAH to current line
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lda hgr_lookup_l,X
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sta GBASL
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lda hgr_lookup_h,X
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clc
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adc HGR_PAGE
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sta GBASH
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;==============
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; current column (work backwards)
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ldy #39 ; 2
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xloop:
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lda #0
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sta COLORS
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; calculate colors
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; color = (XX-FRAME)^(YY)
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;===========================
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; SMALL
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sec ; subtract frame from Y
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tya
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sbc FRAME4
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sta X2
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txa
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eor X2
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and #$2
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beq skip_color_small
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lda #$4c
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; lda #$1b
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sta COLORS
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skip_color_small:
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;===========================
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; MEDIUM
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sec ; subtract frame from Y
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tya
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sbc FRAME2
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sta X2
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txa
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clc
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adc #1
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eor X2
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and #$4
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beq skip_color_medium
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lda #$26
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sta COLORS
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skip_color_medium:
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;===========================
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; LARGE
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sec ; subtract frame from Y
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tya
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sbc FRAME
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sta X2
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txa
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clc
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adc #2
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eor X2
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and #$8
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beq skip_color_large
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lda #$1B
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; lda #$4c
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sta COLORS
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skip_color_large:
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;========================
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; actually draw color
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lda COLORS
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sta (GBASL),Y
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dey ; 1
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bpl xloop ; 2
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dex ; 1
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cpx #$FF
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bne yloop ; 2
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beq parallax_forever ; 2
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; for bot
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; $3F5 - 127 + 3 = $379
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jmp parallax
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