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58 lines
1000 B
ArmAsm
58 lines
1000 B
ArmAsm
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;=======================
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;sin:
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; / 6.28 is roughly the same as *0.16
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; = .5 .25 .125 .0625 .03125
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; 1/6.28 = 0.16 = 0 0 1 0 1 0 0 0 = 0x28
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; i=(i*0x28)>>8;
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; lda IVL,Y ; note, uses absolute as no ZP equiv ; 4
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; sta STEMP1L ; 3
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; lda IVH,Y ; 4
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; A has STEMP1H
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; i2=i<<3;
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asl STEMP1L ; 5
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rol ; 2
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asl STEMP1L ; 5
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rol ; 2
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asl STEMP1L ; 5
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rol ; 2
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; i1=i<<5;
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ldx STEMP1L ; 3
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stx STEMP2L ; 3
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sta STEMP1H ; 3
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asl STEMP2L ; 5
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rol ; 2
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asl STEMP2L ; 5
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rol ; 2
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; i=(i1+i2)>>8;
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; We ignore the low byte as we don't need it
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; possibly inaccurate as we don't clear carry?
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adc STEMP1H ; 2
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tax ; 2
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; sl=fsinh[i];
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; tradeoff size for speed by having lookup
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; table for sign bits
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; the sign lookup only saves like 2 cycles
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; lda sin_table_low,X ; 4+
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; sta OUT1L,Y ; 5
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; lda sin_table_high,X ; 4+
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; sta OUT1H,Y ; 5
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