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**Submitted by Steve Fewell**

**Routine**: anorm[2]

**Name**: Normalise Floating-Point Accumulator (FWA)#2 [only bit-by-bit
method]

**Starting Address**: &81E2

**Entry criteria**: The FWA contains a
floating-point number. Y = Exponent (?&30). A = MSB of FWA's Mantissa
(?&31).

**Exit**: FWA has been normalised

**Description**:

'OR' the Accumulator with 0 to set the status flags according to the value.

If A = Negative then the top bit is set and the FWA is already normalised, so store A & Y back into &31 and &30 (respectively) and exit.

If A is zero then the number in the FWA is considered to be zero, so the FWA's sign, Exponent and Mantissa byte 1 are set to zero to indicate this, and the routine is exited. This uniquely identifies the number zero.

Otherwise, the top bit of the Mantissa is not 1, so we need to normalise the
FWA as follows:

==> Keep
on decrementing the exponent (Y) and multiplying the mantissa by 2 (moving its bits
left a position), until the top bit is set (A becomes negative).

When the number is normalised, store A & Y back into &31 and &30 (respectively) and exit.

**Disassembly for the Normalise FWA#2 [only bit-by-bit method] routine**

81E2 | 009 000 | 09 00 | ORA#&00 | |

81E4 | 0 | 048 012 | 30 0C | BMI 12 --> &81F2 |

81E6 | 240 228 | F0 E4 | BEQ -28 --> &81CC | |

81E8 | 136 | 88 | DEY | |

81E9 | 4 | 006 052 | 06 34 | ASL &34 |

81EB | &3 | 038 051 | 26 33 | ROL &33 |

81ED | &2 | 038 050 | 26 32 | ROL &32 |

81EF | * | 042 | 2A | ROL A |

81F0 | 016 246 | 10 F6 | BPL -10 --> &81E8 | |

81F2 | 1 | 133 049 | 85 31 | STA &31 |

81F4 | 0 | 132 048 | 84 30 | STY &30 |

81F6 | ` | 096 | 60 | RTS |

**Complete Zero Number:**

81CC | d. | 100 046 | 64 2E | STZ &2E |

81CE | d0 | 100 048 | 64 30 | STZ &30 |

81D0 | d/ | 100 047 | 64 2F | STZ &2F |

81D2 | d1 | 100 049 | 64 31 | STZ &31 |

81D4 | ` | 096 | 60 | RTS |