mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-05-29 08:41:36 +00:00
126 lines
1.8 KiB
ArmAsm
126 lines
1.8 KiB
ArmAsm
; thick sine
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; 105 bytes -- original with table sine
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; 89 bytes -- use ROM cosine table to generate sine table
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; 86 bytes -- put sine table in zero page
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; 89 bytes -- adjust to add #1 to avoid thick line at middle
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; 87 bytes -- Y is 0 after HGR2
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; zero page
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sinetable=$70
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HGR_X = $E0
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HGR_XH = $E1
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HGR_Y = $E2
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HGR_COLOR = $E4
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HGR_PAGE = $E6
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SAVEX = $FE
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SAVEY = $FF
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; ROM routines
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HGR2 = $F3D8
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HPOSN = $F411 ; (Y,X),(A) (values stores in HGRX,XH,Y)
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HPLOT0 = $F457 ; plot at (Y,X), (A)
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costable_base = $F5BA
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;================================
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; Clear screen and setup graphics
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;================================
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thick_sine:
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jsr HGR2 ; set hi-res 140x192, page2, fullscreen
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; A and Y both 0 at end
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; try to get sine table from ROM
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rom_sine:
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;==========================================
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; create sinetable using ROM cosine table
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; ldy #0
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ldx #$f
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sinetable_loop:
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lda costable_base+1,Y
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force_zero:
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lsr ; rom value is *256
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lsr ; we want *32
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lsr
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sta sinetable+$10,Y
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sta sinetable+$00,X
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eor #$FF
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sec
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adc #$0
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sta sinetable+$30,Y
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sta sinetable+$20,X
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lda #0 ; hack, ROM cosine table doesn't
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; have a good zero for some reason
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iny
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dex
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beq force_zero
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bpl sinetable_loop
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; x is FF at this point
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;============================
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; main loop
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;============================
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; dex
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stx HGR_COLOR ; required
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; though in emulator it defaults to $FF
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draw_circle:
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ldy #0
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sty SAVEY
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blah_smc:
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ldx #0
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stx SAVEX
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circle_loop:
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lda SAVEX
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and #$3f
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tax
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lda sinetable,X
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; clc
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asl
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; $60 is midscreen
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adc #$60
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ldx SAVEY
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ldy #0
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jsr HPLOT0 ; plot at (Y,X), (A)
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inc SAVEX
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inc SAVEY
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bne circle_loop
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done:
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inc blah_smc+1
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; lda SAVEX
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; and #$3f
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; cmp #$3f
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; bne blah
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bit SAVEX
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bvc blah
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lda HGR_COLOR ; flip draw color $ff/$00/$ff
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eor #$ff
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sta HGR_COLOR
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blah:
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jmp draw_circle
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