wip loop
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mandel.s
242
mandel.s
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@ -1,17 +1,21 @@
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; Our zero-page vars
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sx = $80 ; 8 bits: screen pixel x
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sy = $81 ; 8 bits: screen pixel y
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cx = $82 ; 16 bits fixed point
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cy = $84 ; 16 bits fixed point
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zx = $86 ; 16 bits fixed point
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zy = $88 ; 16 bits fixed point
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zx_2 = $8a ; 32 bits fixed point
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zy_2 = $8e ; 32 bits fixed point
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zx_zy = $92 ; 32 bits fixed point
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dist = $96 ; 32 bits fixed point
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iter = $9a ; 8 bits iteration count
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sx = $80 ; i16: screen pixel x
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sy = $82 ; i16: screen pixel y
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ox = $84 ; fixed3.13: center point x
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oy = $86 ; fixed3.13: center point y
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cx = $84 ; fixed3.13: c_x
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cy = $86 ; fixed3.13: c_y
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zx = $88 ; fixed3.13: z_x
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zy = $8a ; fixed3.13: z_y
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temp = $a0 ; debug temp area
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zx_2 = $90 ; fixed6.26: z_x^2
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zy_2 = $94 ; fixed6.26: z_y^2
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zx_zy = $98 ; fixed6.26: z_x * z_y
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dist = $9c ; fixed6.26: z_x^2 + z_y^2
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iter = $a0 ; u8: iteration count
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zoom = $a1 ; u8: zoom shift level
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temp = $a2 ; u16
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; FP registers in zero page
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FR0 = $d4
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@ -19,6 +23,77 @@ FRE = $da
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FR1 = $e0
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FR2 = $e6
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; High data
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framebuffer_top = $8000
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framebuffer_bottom = $9000
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textbuffer = $9f00
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framebuffer_end = $a000
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height = 184
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half_height = height >> 1
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width = 160
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half_width = 160 >> 1
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width_ratio_3_13 = (5 << 11) ; 5/4
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height_ratio_3_13 = (3 << 11) ; 5/4
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DMACTL = $D400
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DLISTL = $D402
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DLISTH = $D403
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.data
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aspect:
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; aspect ratio!
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; pixels at 320w are 5:6 (narrow)
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; pixels at 160w are 5:3 (wide)
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;
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; cy = (sy << (8 - zoom)) * (96 / 128 = 3 / 4)
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; cx = (sx << (8 - zoom)) * ((3 / 4) * (5 / 3) = 5 / 4)
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;
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; so vertical range -92 .. 91.9 is -2.15625 .. 2.15624
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; &horizontal range -80 .. 79.9 is -3.125 .. 3.124
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;
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; 184h is the equiv of 220.8h at square pixels
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; 320 / 220.8 = 1.45 display aspect ratio
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aspect_x:
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.word 5 << (13 - 2)
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aspect_y:
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.word 3 << (13 - 2)
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bit_masks:
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.byte 3
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.byte 3 << 2
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.byte 3 << 4
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.byte 3 << 6
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display_list:
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; 48 lines overscan
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.repeat 5
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.byte $70 ; 8 blank lines
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.endrep
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; 184 lines graphics
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; ANTIC mode e (160px 2bpp, 1 scan line per line)
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.byte $4e
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.addr framebuffer_top
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.repeat half_height - 1
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.byte $0e
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.endrep
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.byte $4e
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.addr framebuffer_bottom
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.repeat half_height - 1
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.byte $0e
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.endrep
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; 1 line 40-column text
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.byte $42
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.addr textbuffer
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.byte $41 ; jump and blank
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.addr display_list
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.code
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.export start
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@ -181,10 +256,18 @@ positive:
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.macro imul16 dest, arg1, arg2
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copy16 FR0, arg1 ; 12 cyc
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copy16 FR1, arg2 ; 12 cyc
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jsr imul16_func ; 470-780
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jsr imul16_func ; 470-780 cyc
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copy32 dest, FR2 ; 24 cyc
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.endmacro
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.macro imul16_round dest, arg1, arg2
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copy16 FR0, arg1 ; 12 cyc
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copy16 FR1, arg2 ; 12 cyc
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jsr imul16_func ; 470-780 cyc
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round16 FR2 ; 5-28 cyc
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copy16 dest, FR2 + 2 ; 12 cyc
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.endmacro
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; min 470 cycles
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; max 780 cycles
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.proc imul16_func
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@ -269,8 +352,6 @@ next:
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.endmacro
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.proc mandelbrot
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; input:
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; cx: position scaled to 4.12 fixed point - -8..+7.9
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@ -355,29 +436,128 @@ still_in:
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.endproc
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.macro zoom_factor dest, src, zoom, aspect
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.local cont
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.local enough
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; cx = (sx << (8 - zoom))
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copy16 dest, src
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ldx zoom
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cont:
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cpx #8
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beq enough
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shl16 dest
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inx
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jmp cont
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enough:
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; cy = cy * (3 / 4)
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; cx = cx * (5 / 4)
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imul16_round dest, dest, aspect
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.endmacro
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.proc pset
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; screen coords in signed sx,sy
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; iter holds the target to use
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; @todo implement
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rts
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.endproc
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.proc start
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looplong:
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; cx = -0.5
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lda #$f7
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sta cx
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lda #$ff
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sta cx + 1
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; ox = 0; oy = 0; zoom = 0
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lda #0
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sta ox
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sta ox + 1
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sta oy
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sta oy + 1
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sta zoom
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; cy = 1
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lda #$10
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sta cy
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; Disable display DMA
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lda #$00
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sta cy + 1
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sta DMACTL
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jsr mandelbrot
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; should have 32-bit -15 in FR2
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; Set up the display list
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lda #.lobyte(display_list)
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sta DLISTL
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lda #.hibyte(display_list)
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sta DLISTH
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; save the completed iter count for debugging
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lda iter
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; zero the range from framebuffer_top to framebuffer_end
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lda #.lobyte(framebuffer_top)
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sta temp
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lda #.hibyte(framebuffer_top)
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sta temp + 1
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zero_page_loop:
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lda #0
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ldy #0
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zero_byte_loop:
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sta (temp),y
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iny
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bne zero_byte_loop
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inc temp + 1
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lda temp + 1
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cmp #.hibyte(framebuffer_end)
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bne zero_page_loop
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; Re-enable display DMA
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lda #$22
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sta DMACTL
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main_loop:
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; sy = -92 .. 91
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lda #(256-half_height)
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sta sy
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lda #(256-1)
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sta sy + 1
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loop_sy:
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; sx = -80 .. 79
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lda #(256-half_width)
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sta sx
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lda #(256-1)
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sta sx + 1
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loop_sx:
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zoom_factor cx, sx, zoom, aspect_x
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zoom_factor cy, sy, zoom, aspect_y
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jsr mandelbrot
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jsr pset
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lda sx
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clc
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adc #1
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sta sx
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cmp #half_width
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beq loop_sx_done
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lda sx + 1
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adc #0
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sta sx + 1
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jmp loop_sx
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loop_sx_done:
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lda sy
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clc
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adc #1
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sta sy
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cmp #half_height
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beq loop_sy_done
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lda sy + 1
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adc #0
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sta sy + 1
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jmp loop_sy
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loop_sy_done:
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loop:
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; keep looping over so we can work in the debugger
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jmp looplong
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; finished
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jmp loop
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.endproc
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