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229 lines
3.2 KiB
ArmAsm
229 lines
3.2 KiB
ArmAsm
; sierpinski-like demo
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; based on the code from Hellmood's Memories demo
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; by Vince `deater` Weaver <vince@deater.net>
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; the simple sierpinski you more or less just plot
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; X AND Y
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; Hellmood's you plot something more or less like
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; COLOR = ( (Y-(X*T)) & (X+(Y*T) ) & 0xf0
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; where T is an incrementing frame value
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; to get speed on 6502/Apple II we change the multiplies to
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; a series of 16-bit 8.8 fixed point adds
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; TODO:
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; HPLOT timing
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; MOVERIGHT timing
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; MOVERIGHT MOVEDOWN timing
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; LOOKUP TABLE timing
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; zero page
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HGR_BITS = $1C
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GBASH = $27
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MASK = $2E
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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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SAVEX = $F7
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XX_TH = $F8
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XX_TL = $F9
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YY = $FA
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YY_TH = $FB
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YY_TL = $FC
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;T_L = $FD
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;T_H = $FE
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SAVED = $FF
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; Soft switches
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FULLGR = $C052
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PAGE1 = $C054
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PAGE2 = $C055
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LORES = $C056 ; Enable LORES graphics
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; ROM routines
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HGR = $F3E2
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HGR2 = $F3D8
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HPOSN = $F411
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HPLOT0 = $F457
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HPLOT1 = $F45A ; skip the HPOSN call
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COLOR_SHIFT = $F47E ; shift color for odd/even Y (0..7 or 7..13)
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MOVE_RIGHT = $F48A ; move next plot location one to the right
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COLORTBL = $F6F6
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;.zeropage
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;.globalzp T_L,T_H
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;================================
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; Clear screen and setup graphics
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;================================
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sier:
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jsr HGR2 ; set FULLGR, sets A=0
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; lda #0 ; start with multiplier 0
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; sta T_L
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; sta T_H
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sier_outer:
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ldy #0 ; YY starts at 0
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sty YY
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sty YY_TL
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sty YY_TH
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sier_yloop:
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; calc YY_T (8.8 fixed point add)
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; save space by skipping clc as it's only a slight variation w/o
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; clc
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lda YY_TL
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adc T_L
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sta YY_TL
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lda YY_TH
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adc T_H
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sta YY_TH
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; XX in X
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; YY in YY
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ldy #0
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ldx #0 ; XX = 0
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lda YY ; Y co-ord
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jsr HPOSN ; set cursor position to (Y,X), (A)
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; ldy HGR_Y
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; lda GBASH
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;draw_page_smc:
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; adc #0
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; sta GBASH ; adjust for PAGE1/PAGE2 ($400/$800)
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; plp
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; jsr $f806 ; trick to calculate MASK by jumping
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; into middle of PLOT routine
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; reset XX to 0
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ldx #0 ; XX
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stx XX_TL
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stx XX_TH
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sier_xloop:
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stx SAVEX
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; want (YY-(XX*T)) & (XX+(YY*T)
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; SAVED = XX+(Y*T)
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; clc
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txa ; XX
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adc YY_TH
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sta SAVED
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; calc XX*T
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; clc
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lda XX_TL
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adc T_L
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sta XX_TL
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lda XX_TH
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adc T_H
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sta XX_TH
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; calc (YY-X_T)
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lda YY
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sec
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sbc XX_TH
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; want (YY-(XX*T)) & (XX+(YY*T)
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and SAVED
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and #$f0
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beq white
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black:
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lda #0 ; black
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.byte $2C ; bit trick
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white:
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lda #$ff ; white
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color_ready:
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; tax
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; tya
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; lsr ; check even or odd
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; php
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; lda COLORTBL,X
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sta HGR_BITS
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; plp
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; bcc no_shift
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; jsr COLOR_SHIFT ; if odd then color shift
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no_shift:
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jsr HPLOT1 ; plot at current position
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jsr MOVE_RIGHT ; move current position right (trashes A)
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ldx SAVEX ; restore X
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;==================================
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inx ; XX
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bne sier_xloop
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;==================================
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inc YY ; repeat until Y=192
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ldy YY
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cpy #192
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bne sier_yloop
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; inc T
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; clc
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lda T_L
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blah_smc:
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adc #1
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sta T_L
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bcc no_carry
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inc T_H
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no_carry:
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; speed up the zoom as it goes
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inc blah_smc+1
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; x is 48
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;flip_pages:
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; lda draw_page_smc+1 ; DRAW_PAGE
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; beq done_page
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; inx
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;done_page:
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; X=48 ($30) PAGE1=$C054-$30=$C024
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; ldy $C024,X ; set display page to PAGE1 or PAGE2
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; eor #$4 ; flip draw page between $400/$800
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; sta draw_page_smc+1 ; DRAW_PAGE
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jmp sier_outer ; what can we branch on?
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T_L: .byte $00
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T_H: .byte $00
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