89 lines
2.6 KiB
ArmAsm
89 lines
2.6 KiB
ArmAsm
; Math-y functions
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mx %00
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; Special subroutine to divide the accumulator by 164 and return remainder in the Accumulator
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;
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; 164 = $A4 = 1010_0100
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Mod164 cmp #%1010010000000000
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bcc *+5
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sbc #%1010010000000000
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cmp #%0101001000000000
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bcc *+5
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sbc #%0101001000000000
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cmp #%0010100100000000
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bcc *+5
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sbc #%0010100100000000
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cmp #%0001010010000000
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bcc *+5
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sbc #%0001010010000000
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cmp #%0000101001000000
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bcc *+5
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sbc #%0000101001000000
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cmp #%0000010100100000
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bcc *+5
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sbc #%0000010100100000
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cmp #%0000001010010000
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bcc *+5
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sbc #%0000001010010000
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cmp #%0000000101001000
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bcc *+5
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sbc #%0000000101001000
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cmp #%0000000010100100
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bcc *+5
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sbc #%0000000010100100
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rts
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; Special subroutine to divide the accumulator by 208 and return remainder in the Accumulator
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;
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; 208 = $D0 = 1101_0000
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;
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; There are probably faster hacks to divide a 16-bit unsigned value by 208
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; https://www.drdobbs.com/parallel/optimizing-integer-division-by-a-constan/184408499
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; https://embeddedgurus.com/stack-overflow/2009/06/division-of-integers-by-constants/
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Mod208 cmp #%1101000000000000
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bcc *+5
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sbc #%1101000000000000
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cmp #%0110100000000000
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bcc *+5
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sbc #%0110100000000000
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cmp #%0011010000000000
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bcc *+5
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sbc #%0011010000000000
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cmp #%0001101000000000
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bcc *+5
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sbc #%0001101000000000
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cmp #%0000110100000000
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bcc *+5
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sbc #%0000110100000000
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cmp #%0000011010000000
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bcc *+5
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sbc #%0000011010000000
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cmp #%0000001101000000
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bcc *+5
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sbc #%0000001101000000
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cmp #%0000000110100000
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bcc *+5
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sbc #%0000000110100000
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cmp #%0000000011010000
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bcc *+5
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sbc #%0000000011010000
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rts
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