123 lines
1.9 KiB
ArmAsm
123 lines
1.9 KiB
ArmAsm
; Tilted Plane, based on the code in Hellmood's Memories
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; by deater (Vince Weaver) <vince@deater.net>
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; Zero Page
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BASL = $28
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BASH = $29
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H2 = $2C
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COLOR = $30
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X1 = $F0
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X2 = $F1
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Y1 = $F2
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Y2 = $F3
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M1 = $F7
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M2 = $F8
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TEMP = $FA
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TEMPY = $FB
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FRAME = $FC
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TEMPX = $FD
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SCALED = $FE
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; Soft Switches
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KEYPRESS= $C000
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KEYRESET= $C010
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SET_GR = $C050 ; Enable graphics
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FULLGR = $C052 ; Full screen, no text
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PAGE0 = $C054 ; Page0
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PAGE1 = $C055 ; Page1
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LORES = $C056 ; Enable LORES graphics
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; ROM routines
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PLOT = $F800 ; plot, horiz=y, vert=A (A trashed, XY Saved)
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SETCOL = $F864
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TEXT = $FB36 ;; Set text mode
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BASCALC = $FBC1
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SETGR = $FB40
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HOME = $FC58 ;; Clear the text screen
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WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
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HLINE = $F819
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tilted_plane:
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;===================
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; init screen
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jsr SETGR ; 3
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bit FULLGR ; 3
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jsr init_multiply_tables
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plane_forever:
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inc FRAME ; 2
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ldx #47 ; yy ; 2
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yloop:
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ldy #39 ; xx ; 2
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xloop:
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; clc
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; adc #$10 ; adjust top of screen
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lda division,X ; scaled=((0x3d5/yy)&0xff);
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; reverse divide AL=C/Y'
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sta M1
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; color=((signed char)((xprime-20)&0xff))*((signed char)(scaled&0xff));
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tya
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sec
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sbc #20
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sta M2
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jsr multiply_s8x8
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lda M1
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ror M2
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ror
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ror M2
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ror
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and #$f
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sta COLOR
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; color=(color>>6)&0xff;
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sec
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lda SCALED
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sbc FRAME ; scaled-=frame;
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eor COLOR ; color^=(scaled&0xff);
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and #$1C ; color&=0x1c; // map colors
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jsr SETCOL
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txa ; A==Y1 ; 1
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jsr PLOT ; (X2,Y1) ; 3
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dey ; 1
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bpl xloop ; 2
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dex ; 1
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bpl yloop ; 2
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bmi plane_forever ; 2
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division:
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.byte $62,$59,$51,$4B,$46,$41,$3D,$39,$36,$33
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.byte $31,$2E,$2C,$2A,$28,$27,$25,$24,$23,$21
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.byte $20,$1F,$1E,$1D,$1C,$1C,$1B,$1A,$19,$19
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.byte $18,$17,$17,$16,$16,$15,$15,$14,$14,$14
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.byte $13,$13,$12,$12,$12,$11,$11,$11
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.include "multiply_tables.s"
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.include "multiply_s8x8.s"
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.include "multiply_u8x8.s"
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