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477
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1 * Did mods as per Chris Dekker's RUNB
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2 L4234 comb Default to divide by 0 error
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3 ldb #$2D
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4 tst 2,y Is number to divide by 0?
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5 beq L4233 Yes, return with error
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6 tst 8,y Is dividend=0?
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7 lbeq L40DD Yes, answer=0, return from there
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8 lda 7,y Get exponent of # to dividend
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9 suba 1,y Subtract exponent of divisor
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10 lbvs L40EF
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11 sta 7,y
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12 lda #$21 ??? (count for exponent shifts?)
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13 ldb 5,y Get sign byte of dividend
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14 eorb $B,y Calculate which sign result will be
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15 andb #1 Just keep sign bit
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16 std ,y Save ??? & resulting sign
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17 ldq 2,y Divide whole divisor mantissa by 2
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18 lsrd /
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19 rorw < these both eat sign bit and make mantissa a
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20 stq 2,y \ 31 bit number
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21 ldq 8,y Divide whole dividend by 2
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22 lsrd
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23 rorw
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24 clr $B,y Clear last byte of dividend mantissa
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25 L426F subw 4,y Subtract divisor from dividend
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26 sbcd 2,y
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27 beq L42AB
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28 bmi L42A7
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29 L427E orcc #1
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30 L4280 dec ,y
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31 beq L42F8
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32 rol $B,y
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33 rol $A,y
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34 rol 9,y
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35 rol 8,y
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36 andcc #$fe
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37 rolw
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38 rold
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39 bcc L426F
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40 addw 4,y
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41 adcd 2,y
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42 beq L42AB
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43 bpl L427E
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44 L42A7 andcc #$FE
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45 bra L4280
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46
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47 L42AB tstw
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48 bne L427E
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49 ldb ,y
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50 decb
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51 subb #$10
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52 blt L42CD
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53 subb #$08
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54 blt L42C2
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55 stb ,y
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56 lda $B,y
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57 ldb #$80
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58 andcc #$fe
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59 bra L42EB
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60
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61 L42C2 addb #$08
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62 stb ,y
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63 ldw #$8000
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64 ldd $A,y
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65 andcc #$fe
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66 bra L42EB
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67
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68 L42CD addb #$08
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69 blt L42DB
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70 stb ,y
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71 ldq 9,y
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72 ldf #$80
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73 andcc #$fe
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74 bra L42EB
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75
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76 L42DB addb #$07
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77 stb ,y
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78 ldq 8,y
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79 orcc #$01
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80 L42E5 rolw
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81 rold
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82 L42EB dec ,y
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83 bpl L42E5
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84 tsta
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85 bra L42FC
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86
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87 L42F8 ldq 8,y
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88 L42FC bmi L430C
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89 rolw
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90 rold
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91 dec 7,y
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92 lbvs L40DD
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93 L430C addw #1
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94 adcd #0
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95 bcc L4321
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96 rora
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97 inc 7,y
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98 lbvs L40DD
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99 L4321 std 8,y
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100 tfr w,d
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101 lsrb Shift out sign bit
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102 lslb
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103 orb 1,y Merge in result's sign
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104 std $A,y
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105 inc 7,y
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106 lbvs L40EF
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107 L4331 leay 6,y Eat temp var
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108 rts & return
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109
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