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68 lines
949 B
ArmAsm
68 lines
949 B
ArmAsm
; table look up sine
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; trying to make a 64 entry 32*sin() in the zero page
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; want to beat 35 bytes (that's what the cos/ROM does)
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; 57 bytes -- original
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; 48 bytes -- optimize
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; 46 bytes -- zero page
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; zero page
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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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FRAME = $FC
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SUM = $FD
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SAVEX = $FE
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SAVEY = $FF
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sinetable=$70
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table_sine:
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;==================
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; create sinetable
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ldx #0 ; Y is 0
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ldy #$10
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sinetable_loop:
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lda sinetable_base,X ; 4+
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sta sinetable+$10,X
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sta sinetable+$00,Y
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eor #$ff
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sec ; these maybe not needed
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adc #$0
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sta sinetable+$30,X
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sta sinetable+$20,Y
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inx
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dey
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bpl sinetable_loop
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; Y is 0 at this point?
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done:
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jmp done
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sinetable_base:
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; this is actually (32*sin(x))
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;.byte $00,$03,$06,$09,$0C,$0F,$11,$14
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;.byte $16,$18,$1A,$1C,$1D,$1E,$1F,$1F,$20
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.byte $20,$1F,$1F,$1E,$1D,$1C,$1A,$18,$16
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.byte $14,$11,$0F,$0C,$09,$06,$03,$00
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