base:16bit_multiplication_32-bit_product

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base:16bit_multiplication_32-bit_product [2015-04-17 04:30] 127.0.0.1 external edit |
base:16bit_multiplication_32-bit_product [2018-09-04 23:32] (current) agentfriday Readability (syntax highlighting, indents) |
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====== 16-bit multiply with 32-bit product | ====== 16-bit multiply with 32-bit product | ||

- | < | + | <6502acme> |

;16-bit multiply with 32-bit product | ;16-bit multiply with 32-bit product | ||

;took from 6502.org | ;took from 6502.org | ||

- | multiplier = $f7 | + | multiplier = $f7 |

- | multiplicand = $f9 | + | multiplicand = $f9 |

- | product = $fb | + | product = $fb |

- | mult16 lda #$00 | + | mult16 lda #$00 |

- | sta product+2 ; clear upper bits of product | + | sta product+2 ; |

- | sta product+3 | + | sta product+3 |

- | ldx #$10 ; set binary count to 16 | + | ldx #$10 ; set binary count to 16 |

- | shift_r lsr multiplier+1 ; divide multiplier by 2 | + | shift_r lsr multiplier+1 ; |

- | ror multiplier | + | ror multiplier |

- | bcc rotate_r | + | bcc rotate_r |

- | lda product+2 ; get upper half of product and add multiplicand | + | lda product+2 ; |

- | clc | + | clc |

- | adc multiplicand | + | adc multiplicand |

- | sta product+2 | + | sta product+2 |

- | lda product+3 | + | lda product+3 |

- | adc multiplicand+1 | + | adc multiplicand+1 |

- | rotate_r ror ; rotate partial product | + | rotate_r ror ; rotate partial product |

- | sta product+3 | + | sta product+3 |

- | ror product+2 | + | ror product+2 |

- | ror product+1 | + | ror product+1 |

- | ror product | + | ror product |

- | dex | + | dex |

- | bne shift_r | + | bne shift_r |

- | rts | + | rts |

</ | </ | ||

+ |

base/16bit_multiplication_32-bit_product.txt · Last modified: 2018-09-04 23:32 by agentfriday