mirror of
https://github.com/JohnSnape/6502code.git
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27 lines
1.4 KiB
Plaintext
27 lines
1.4 KiB
Plaintext
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2000- 5
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0000- 6 MUL1L .EQ $00 ;Multiplicand
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0001- 7 MUL1H .EQ $01
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0002- 8 MUL2L .EQ $02 ;Multiplier
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0003- 9 MUL2H .EQ $03
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0004- 10 RSLTL .EQ $04 ;Result
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0005- 11 RSLTH .EQ $05
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2000- 12
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2000-A0 10 13 ( 2) RMUL LDY #16 16-BIT MULTIPLIER
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2002-A5 00 14 ( 3) .1 LDA MUL1L (MUL1 * MUL2) + RSLT
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2004-4A 15 ( 2) LSR CHECK NEXT BIT OF MULTIPLIER
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2005-90 0D 16 (2**) BCC .2 IF ZERO, DON'T ADD MULTIPLICAND
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2007-18 17 ( 2) CLC ADD MULTIPLICAND TO PARTIAL PRODUCT
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2008-A5 02 18 ( 3) LDA MUL2L
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200A-65 04 19 ( 3) ADC RSLTL
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200C-85 02 20 ( 2) STA MUL2L
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200E-A5 03 21 ( 3) LDA MUL2H
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2010-65 05 22 ( 3) ADC RSLTH
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2012-85 03 23 ( 2) STA MUL2H
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2014-66 03 24 ( 5) .2 ROR MUL2H SHIFT PARTIAL PRODUCT
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2016-66 02 25 ( 5) ROR MUL2L
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2018-66 01 26 ( 5) ROR MUL1H
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201A-66 00 27 ( 5) ROR MUL1L
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201C-88 28 ( 2) DEY NEXT BIT
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201D-D0 E3 29 (2**) BNE .1 UNTIL ALL 16
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201F-60 30 ( 6) RTS
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