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1 ;=============================================================================
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2 ;
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634
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3 ; File math.asm * combined next generation V3.09.4k
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4 ;
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5 ; Math subroutines
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6 ;
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7 ; Copyright (c) 2011, JD Gascuel, HeinrichsWeikamp, all right reserved.
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8 ;=============================================================================
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9 ; HISTORY
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10 ; 2011-08-03 : [mH] moving from OSTC code
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11
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12
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623
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13 #include "hwos.inc" ; mandatory header
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14
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604
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15
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16 ;=============================================================================
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634
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17 math1 CODE
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18 ;=============================================================================
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604
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19
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634
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20 ;-----------------------------------------------------------------------------
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21 ; Divide a 16 Bit Integer by a Power of 2: divA:2 = divA:2 / 2^WREG
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22 ;
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23 ; trashes WREG
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24 ;
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25 global div16
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26 div16:
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27 bcf STATUS,C ; clear carry
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28 rrcf divA+1 ; rotate right high byte, carry into MSB, LSB into carry
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29 rrcf divA+0 ; rotate right low byte, carry into MSB, LSB into carry
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30 decfsz WREG ; decrement counter, done?
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31 bra div16 ; NO - loop
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32 return ; YES - done
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33
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34
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634
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35 ;=============================================================================
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36 math2 CODE
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37 ;=============================================================================
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38
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39 ;-----------------------------------------------------------------------------
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40 ; Multiply a 16 bit Integer by a Power of 2: xA:2 = xA:2 * 2^WREG
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41 ;
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42 ; trashes WREG
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43 ;
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44 global mult16
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45 mult16:
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46 bcf STATUS,C ; clear carry
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47 rlcf divA+0,F ; rotate left low byte, carry into LSB, MSB into carry
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48 rlcf divA+1,F ; rotate left high byte, carry into LSB, MSB into carry
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49 decfsz WREG ; decrement counter, done?
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50 bra mult16 ; NO - loop
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51 return ; YES - done
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52
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53
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634
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54 ;=============================================================================
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55 math3 CODE
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56 ;=============================================================================
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57
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58 ;-----------------------------------------------------------------------------
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59 ; Add two UNSIGNED 16 bit Integers: sub_c:2 = sub_a:2 + sub_b:2
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60 ;
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61 ; trashes WREG
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62 ;
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63 global addU16
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628
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64 addU16:
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65 movf sub_a+0,W ; get 1st summand (low byte) to WREG
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66 addwf sub_b+0,W ; add 2nd summand (low byte) and store result in WREG
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67 movwf sub_c+0 ; copy result (low byte) to sub_c
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68 movf sub_a+1,W ; get 1st summand (high byte) to WREG
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69 addwfc sub_b+1,W ; add 2nd summand (high byte) and store result in WREG
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70 movwf sub_c+1 ; copy result (high byte) to sub_c
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71 return ; done
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72
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73
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634
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74 ;=============================================================================
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75 math4 CODE
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76 ;=============================================================================
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77
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78 ;-----------------------------------------------------------------------------
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79 ; Subtract two SIGNED 16 Bit Integers: sub_c:2 = sub_a:2 - sub_b:2
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80 ;
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81 ; sets neg_flag if result is < 0, trashes WREG
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82 ;
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83 global sub16
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84 sub16:
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85 bcf neg_flag ; clear flag which will indicate if result is negative
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86 movf sub_b+0,W ; get value to be subtracted, low byte
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87 subwf sub_a+0,W ; execute subtraction on low byte
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88 movwf sub_c+0 ; copy result to output variable, low byte
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89 movf sub_b+1,W ; get value to be subtracted, high byte
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90 subwfb sub_a+1,W ; execute subtraction on high byte, considering borrow flag
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91 movwf sub_c+1 ; copy result to output variable, high byte
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92 btfss STATUS,N ; result negative ?
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93 return ; NO - result positive, done
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94 bsf neg_flag ; YES - set flag
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95 comf sub_c+1 ; - do a 16 bit sign change
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96 negf sub_c+0 ;
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97 btfsc STATUS,C ; - carry to be propagated ?
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98 incf sub_c+1,F ; YES - do it
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99 return ; - done
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100
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101
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634
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102 ;=============================================================================
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103 math5 CODE
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104 ;=============================================================================
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105
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106 ;-----------------------------------------------------------------------------
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107 ; Subtract two UNSIGNED 16 Bit Integers: sub_c:2 = sub_a:2 - sub_b:2
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108 ;
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109 ; sets neg_flag if result is < 0, trashes WREG
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110 ;
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111 global subU16
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112 subU16:
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113 bcf neg_flag ; clear flag which will indicate if result is negative
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114 movf sub_b+0,W ; get value to be subtracted, low byte
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604
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115 subwf sub_a+0,W ; execute subtraction on low byte
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116 movwf sub_c+0 ; copy result to output variable, low byte
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117 movf sub_b+1,W ; get value to be subtracted, high byte
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118 subwfb sub_a+1,W ; execute subtraction on high byte, considering borrow flag
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119 movwf sub_c+1 ; copy result to output variable, high byte
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120 btfsc STATUS,C ; borrow to propagate (B == /CARRY) ?
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121 return ; NO - result positive, done
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122 bsf neg_flag ; YES - set flag
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123 comf sub_c+1 ; - do a 16 bit sign change
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124 negf sub_c+0 ; - ...
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604
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125 btfsc STATUS,C ; - carry to be propagated ?
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126 incf sub_c+1,F ; YES - do it
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127 return ; - done
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128
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0
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129
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634
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130 ;=============================================================================
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131 math6 CODE
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132 ;=============================================================================
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133
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134 ;-----------------------------------------------------------------------------
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135 ; Compare two UNSIGNED 16 Bit Integers: sub_a:2 - sub_b:2
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136 ;
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137 ; sets neg_flag if result is < 0, trashes WREG
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138 ; the subtraction result is not stored
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139 ;
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140 global cmpU16
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623
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141 cmpU16:
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142 bcf neg_flag ; clear flag which will indicate if result is negative
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143 movf sub_b+0,W ; get value to be subtracted, low byte
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144 subwf sub_a+0,W ; execute subtraction on low byte
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145 movf sub_b+1,W ; get value to be subtracted, high byte
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146 subwfb sub_a+1,W ; execute subtraction on high byte, considering borrow flag
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147 btfss STATUS,C ; borrow to propagate (B == /CARRY) ?
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148 bsf neg_flag ; YES - result is negative, set flag
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149 return ; done
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150
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151
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634
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152 ;=============================================================================
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153 math7 CODE
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154 ;=============================================================================
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155
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156 ;-----------------------------------------------------------------------------
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157 ; Multiply two UNSIGNED 16 bit Integers: xC:4 = xA:2 * xB:2
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158 ;
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159 ; trashes PRODL, PRODH, WREG
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160 ;
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161 global mult16x16
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604
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162 mult16x16:
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163 clrf xC+2 ; clear the high-order bits
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634
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164 clrf xC+3 ; ...
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165
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604
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166 movf xA+0,W ; do the "L" multiplication
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167 mulwf xB+0
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168 movff PRODL,xC+0 ; copy result to xC
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169 movff PRODH,xC+1
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634
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170
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604
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171 movf xA+0,W ; do the "I" multiplication
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172 mulwf xB+1
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173 movf PRODL,W ; get the product's low byte...
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174 addwf xC+1,F ; ... and add it to xC+1
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175 movf PRODH,W ; get the product's high byte...
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176 addwfc xC+2,F ; ... and add it to xC+2 obeying carry bit from xC+1
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634
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177
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604
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178 movf xA+1,W ; do the "O" multiplication
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179 mulwf xB+0
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634
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180 movf PRODL,W ; get the product's low byte...
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604
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181 addwf xC+1,F ; ... and add it to xC+1
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182 movf PRODH,W ; get the product's high byte...
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183 addwfc xC+2,F ; ... and add it to xC+2 obeying carry bit from xC+1
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184 clrf WREG ; clear WREG...
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185 addwfc xC+3,F ; ... add add it to xC+3 obeying carry bit from xC+2 (can only happen in "O" multiplication)
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634
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186
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604
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187 movf xA+1,W ; do the "F" multiplication
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188 mulwf xB+1
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634
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189 movf PRODL,W ; get the product's low byte...
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604
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190 addwf xC+2,F ; ... and add it to xC+2
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191 movf PRODH,W ; get the product's high byte...
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192 addwfc xC+3,F ; ... and add it to xC+3 obeying carry bit from xC+2
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634
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193
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194 return ; done
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0
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195
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196
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634
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197 ;=============================================================================
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198 math8 CODE
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199 ;=============================================================================
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200
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201 ;-----------------------------------------------------------------------------
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202 ; Divide two UNSIGNED 16 Bit Integers: xC:2 = xA:2 / xB:2 with xA as remainder
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203 ;
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204 ; trashes WREG
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205 ;
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206 global div16x16
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604
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207 div16x16:
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208 movlw .16 ; process 16 bits ...
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209 movwf math_loop ; ... initialize loop counter
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210 movff xA+0,xC+0 ; copy xA to xC
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211 movff xA+1,xC+1 ; ...
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212 clrf xA+0 ; clear xA, will now be used to hold the remainder
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213 clrf xA+1 ; ...
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214 div16x16_1:
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215 bcf STATUS,C ; clear carry flag to shift in a zero bit
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216 rlcf xC+0,F ; shift left xC
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217 rlcf xC+1,F ; ... shifting MSB out of xC...
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218 rlcf xA+0,F ; ... and into LSB of xA
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219 rlcf xA+1,F ; ...
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220 btfsc STATUS,C ; did the remainder overflow (carry set)?
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221 bra div16x16_2 ; YES - directly generate a result bit = 1
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222 movf xB+0,W ; NO - compute remainder - divisor = xA - xB, trash result to WREG
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223 subwf xA+0,W ; - ...
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224 movf xB+1,W ; - ...
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225 subwfb xA+1,W ; - ...
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226 btfss STATUS,C ; - remainder < divisor (-> borrow flag set, equals carry flag cleared) ?
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227 bra div16x16_3 ; YES - result bit = 0, keep LSB of xC+0 being 0
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228 div16x16_2:
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229 bsf xC+0,0 ; NO - result bit = 1, set LSB of xC+0 to 1
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230 movf xB+0,W ; - subtract divisor from remainder "for real": xA = xA - xB
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231 subwf xA+0,F ; - ...
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232 movf xB+1,W ; - ...
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233 subwfb xA+1,F ; - ...
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0
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234 div16x16_3:
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604
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235 decfsz math_loop,F ; decrement loop counter, all bits done?
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236 bra div16x16_1 ; NO - loop
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237 return ; YES - done
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0
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238
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239
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634
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240 ;=============================================================================
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241 math9 CODE
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242 ;=============================================================================
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243
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244 ;-----------------------------------------------------------------------------
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245 ; Divide a 32 Bit Integer by a 16 Bit Integer: xC:4 = xC:4 / xB:2 with xA as remainder
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246 ;
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247 ; trashes WREG
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248 ;
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249 global div32x16
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604
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250 div32x16:
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251 movlw .32 ; process 32 bits ...
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252 movwf math_loop ; ... initialize loop counter
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253 clrf xA+0 ; clear xA, will be used to hold the remainder
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254 clrf xA+1 ; ...
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255 div32x16_1:
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256 bcf STATUS,C ; clear carry flag to shift in a zero bit
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257 rlcf xC+0,F ; shift left xC
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258 rlcf xC+1,F ; ...
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259 rlcf xC+2,F ; ...
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260 rlcf xC+3,F ; ... shifting MSB out of xC...
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261 rlcf xA+0,F ; ... and into LSB of xA
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262 rlcf xA+1,F ; ...
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263 btfsc STATUS,C ; did the remainder overflow (carry set)?
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264 bra div32x16_2 ; YES - directly generate a result bit = 1
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265 movf xB+0,W ; NO - compute remainder - divisor = xA - xB, trash result to WREG
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266 subwf xA+0,W ; - ...
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267 movf xB+1,W ; - ...
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268 subwfb xA+1,W ; - ...
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269 btfss STATUS,C ; - remainder < divisor (-> borrow flag set, equals carry flag cleared) ?
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270 bra div32x16_3 ; YES - result bit = 0, keep LSB of xC+0 being 0
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0
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271 div32x16_2:
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604
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272 bsf xC+0,0 ; NO - result bit = 1, set LSB of xC+0 to 1
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273 movf xB+0,W ; - subtract divisor from remainder "for real": xA = xA - xB
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274 subwf xA+0,F ; - ...
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275 movf xB+1,W ; - ...
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276 subwfb xA+1,F ; - ...
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0
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277 div32x16_3:
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604
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278 decfsz math_loop,F ; decrement loop counter, all bits done?
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279 bra div32x16_1 ; NO - loop
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280 return ; YES - done
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281
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282
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634
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283 ;-----------------------------------------------------------------------------
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284 ;
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285 ; ISR math functions
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286 ;
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287 ;-----------------------------------------------------------------------------
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288
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289 ;=============================================================================
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290 math10 CODE
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604
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291 ;=============================================================================
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292
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634
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293 ;-----------------------------------------------------------------------------
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294 ; 24 Bit Shift, repeated WREG Times, dedicated to a specific Usage
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295 ;
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296 ; Because less than 8 bits are shifted and only C[2:1] is needed,
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297 ; we don't care what bit is inserted.
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298 ;
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299 global isr_shift_C31
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604
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300 isr_shift_C31:
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301 rrcf isr_xC+3,F ; shift three bytes
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634
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302 rrcf isr_xC+2,F ; ...
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303 rrcf isr_xC+1,F ; ...
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604
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304 decfsz WREG ; decrement loop counter, done?
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305 bra isr_shift_C31 ; NO - loop
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306 return ; YES - done
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307
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308
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634
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309 ;=============================================================================
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310 math11 CODE
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311 ;=============================================================================
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312
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313 ;-----------------------------------------------------------------------------
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314 ; Multiply two UNSIGNED 16 Bit Integers: isr_xC = isr_xA * isr_xB
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315 ;
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316 ; trashes PRODL, PRODH, WREG
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317 ;
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318 global isr_unsigned_mult16x16
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604
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319 isr_unsigned_mult16x16:
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320 movf isr_xA+0,W ; multiply a[0] * b[0]
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634
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321 mulwf isr_xB+0 ; ...
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604
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322 movff PRODL,isr_xC+0 ; store product to c[1]:c[0]
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634
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323 movff PRODH,isr_xC+1 ; ...
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324
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604
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325 movf isr_xA+1,W ; multiply a[1] * b[1]
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634
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326 mulwf isr_xB+1 ; ...
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604
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327 movff PRODL, isr_xC+2 ; store product to c[3]:c[2]
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634
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328 movff PRODH, isr_xC+3 ; ...
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329
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604
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330 movf isr_xA+0,W ; multiply a[0] * b[1]
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634
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331 mulwf isr_xB+1 ; ...
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604
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332 movf PRODL,W ; add cross product to c[3]:c[2]:c[1]
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634
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333 addwf isr_xC+1,F ; ...
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334 movf PRODH,W ; ...
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604
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335 addwfc isr_xC+2,F ; propagate carry
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634
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336 clrf WREG ; ...
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337 addwfc isr_xC+3,F ; ...
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338
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604
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339 movf isr_xA+1,W ; multiply a[1] * b[0]
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634
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340 mulwf isr_xB+0 ; ...
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604
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341 movf PRODL,W ; add cross product
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634
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342 addwf isr_xC+1,F ; ...
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343 movf PRODH,W ; ...
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604
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344 addwfc isr_xC+2,F ; propagate carry
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634
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345 clrf WREG ; ...
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346 addwfc isr_xC+3,F ; ...
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347 return ; done
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0
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348
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643
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349 ;=============================================================================
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350 math12 CODE
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351 ;=============================================================================
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0
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352
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634
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353 ;-----------------------------------------------------------------------------
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354 ; Multiply two SIGNED 16 Bit Integers: isr_xC = isr_xA * isr_xB
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355 ;
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356 ; trashes PRODL, PRODH, WREG
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357 ;
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358 global isr_signed_mult16x16
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604
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359 isr_signed_mult16x16:
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634
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360 ; do an unsigned multiplication first
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643
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361 call isr_unsigned_mult16x16
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634
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362
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363 ; manage sign extension of operand B
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604
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364 btfss isr_xB+1,7 ; is B negative ?
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365 bra isr_signed_mult_checkA ; NO - continue checking operand A
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634
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366 movf isr_xA+0,W ; YES - add -65536 * A
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367 subwf isr_xC+2,F ; - ...
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368 movf isr_xA+1,W ; - ...
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369 subwfb isr_xC+3,F ; - ...
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643
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370 isr_signed_mult_checkA: ; manage sign extension of operand B
|
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604
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371 btfss isr_xA+1,7 ; is A negative ?
|
|
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372 return ; NO - done
|
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634
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373 movf isr_xB+0,W ; YES - add -65536 * B
|
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374 subwf isr_xC+2,F ; - ...
|
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375 movf isr_xB+1,W ; - ...
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376 subwfb isr_xC+3,F ; - ...
|
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377 return ; - done
|
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378
|
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643
|
379 ;=============================================================================
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380 math13 CODE
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|
381 ;=============================================================================
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382
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383 ;-----------------------------------------------------------------------------
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384 ; Multiply two UNSIGNED 24 Bit Integers: isr_xC = isr_xA * isr_xB
|
|
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385 ;
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386 ; trashes PRODL, PRODH, WREG
|
|
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387 ;
|
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388 global isr_unsigned_mult24x24
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|
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389 isr_unsigned_mult24x24:
|
|
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390 call isr_unsigned_mult16x16 ; Do the 16x16 first
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|
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391 clrf isr_xC+4
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|
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392 clrf isr_xC+5 ; clear upper 16 bit
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|
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393 ; do the remaining three multiplications
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394 movf isr_xA+0,W ; multiply a[0] * b[2]
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395 mulwf isr_xB+2 ; ...
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|
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396 movf PRODL,W ; add cross product to c[4]:c[3]:c[2]
|
|
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397 addwf isr_xC+2,F ; ...
|
|
|
398 movf PRODH,W ; ...
|
|
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399 addwfc isr_xC+3,F ; propagate carry
|
|
|
400 clrf WREG ; ...
|
|
|
401 addwfc isr_xC+4,F ; ...
|
|
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402 addwfc isr_xC+5,F ; ...
|
|
|
403
|
|
|
404 movf isr_xA+2,W ; multiply a[2] * b[0]
|
|
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405 mulwf isr_xB+0 ; ...
|
|
|
406 movf PRODL,W ; add cross product to c[4]:c[3]:c[2]
|
|
|
407 addwf isr_xC+2,F ; ...
|
|
|
408 movf PRODH,W ; ...
|
|
|
409 addwfc isr_xC+3,F ; propagate carry
|
|
|
410 clrf WREG ; ...
|
|
|
411 addwfc isr_xC+4,F ; ...
|
|
|
412 addwfc isr_xC+5,F ; ...
|
|
|
413 ; isr_xC[2] done.
|
|
|
414
|
|
|
415 movf isr_xA+2,W ; multiply a[2] * b[1]
|
|
|
416 mulwf isr_xB+1 ; ...
|
|
|
417 movf PRODL,W ; add cross product to c[5]:c[4]:c[3]
|
|
|
418 addwf isr_xC+3,F ; ...
|
|
|
419 movf PRODH,W ; ...
|
|
|
420 addwfc isr_xC+4,F ; propagate carry
|
|
|
421 clrf WREG ; ...
|
|
|
422 addwfc isr_xC+5,F ; ...
|
|
|
423
|
|
|
424 movf isr_xA+1,W ; multiply a[1] * b[2]
|
|
|
425 mulwf isr_xB+2 ; ...
|
|
|
426 movf PRODL,W ; add cross product to c[5]:c[4]:c[3]
|
|
|
427 addwf isr_xC+3,F ; ...
|
|
|
428 movf PRODH,W ; ...
|
|
|
429 addwfc isr_xC+4,F ; propagate carry
|
|
|
430 clrf WREG ; ...
|
|
|
431 addwfc isr_xC+5,F ; ...
|
|
|
432 ; isr_xC[3] done.
|
|
|
433
|
|
|
434 movf isr_xA+2,W ; multiply a[2] * b[2]
|
|
|
435 mulwf isr_xB+2 ; ...
|
|
|
436 movf PRODL,W ; add cross product to c[5]:c[4]
|
|
|
437 addwf isr_xC+4,F ; ...
|
|
|
438 movf PRODH,W ; ...
|
|
|
439 addwfc isr_xC+5,F ; propagate carry
|
|
|
440 ; isr_xC[4] done.
|
|
|
441 ; isr_xC[5] done.
|
|
|
442
|
|
|
443 return ; done
|
|
|
444
|
|
|
445 ;=============================================================================
|
|
|
446 math14 CODE
|
|
|
447 ;=============================================================================
|
|
|
448
|
|
|
449 ;-----------------------------------------------------------------------------
|
|
|
450 ; Multiply two UNSIGNED Integers (32 and 24 Bit): isr_xC = isr_xA * isr_xB
|
|
|
451 ;
|
|
|
452 ; trashes PRODL, PRODH, WREG
|
|
|
453 ;
|
|
|
454 global isr_unsigned_mult32x24
|
|
|
455 isr_unsigned_mult32x24:
|
|
|
456 call isr_unsigned_mult24x24 ; Do the 24x24 first
|
|
|
457 clrf isr_xC+6 ; clear upper 8 bit
|
|
|
458 ; do the remaining three multiplications
|
|
|
459 movf isr_xA+3,W ; multiply a[3] * b[0]
|
|
|
460 mulwf isr_xB+0 ; ...
|
|
|
461 movf PRODL,W ; add cross product to c[5]:c[4]:c[3]
|
|
|
462 addwf isr_xC+3,F ; ...
|
|
|
463 movf PRODH,W ; ...
|
|
|
464 addwfc isr_xC+4,F ; propagate carry
|
|
|
465 clrf WREG ; ...
|
|
|
466 addwfc isr_xC+5,F ; ...
|
|
|
467 addwfc isr_xC+6,F ; ...
|
|
|
468 ; isr_xC[3] done.
|
|
|
469
|
|
|
470 movf isr_xA+3,W ; multiply a[3] * b[1]
|
|
|
471 mulwf isr_xB+1 ; ...
|
|
|
472 movf PRODL,W ; add cross product to c[5]:c[4]
|
|
|
473 addwf isr_xC+4,F ; ...
|
|
|
474 movf PRODH,W ; ...
|
|
|
475 addwfc isr_xC+5,F ; propagate carry
|
|
|
476 clrf WREG ; ...
|
|
|
477 addwfc isr_xC+6,F ; ...
|
|
|
478 ; isr_xC[4] done.
|
|
|
479
|
|
|
480 movf isr_xA+3,W ; multiply a[3] * b[2]
|
|
|
481 mulwf isr_xB+2 ; ...
|
|
|
482 movf PRODL,W ; add cross product to c[5]:c[4]
|
|
|
483 addwf isr_xC+5,F ; ...
|
|
|
484 movf PRODH,W ; ...
|
|
|
485 addwfc isr_xC+6,F ; propagate carry
|
|
|
486 ; isr_xC[5] done.
|
|
|
487 ; isr_xC[6] done.
|
|
|
488 return ; done
|
|
|
489
|
|
|
490
|
|
|
491 ;=============================================================================
|
|
|
492 math15 CODE
|
|
|
493 ;=============================================================================
|
|
|
494
|
|
|
495 ;-----------------------------------------------------------------------------
|
|
|
496 ; Multiply two SIGNED 24 Bit Integers: isr_xC = isr_xA * isr_xB
|
|
|
497 ;
|
|
|
498 ; trashes PRODL, PRODH, WREG
|
|
|
499 ;
|
|
|
500 global isr_signed_mult24x24
|
|
|
501 isr_signed_mult24x24:
|
|
|
502 ; do an unsigned multiplication first
|
|
|
503 call isr_unsigned_mult24x24
|
|
|
504
|
|
|
505 ; manage sign extension of operand B
|
|
|
506 btfss isr_xB+2,7 ; is B negative ?
|
|
|
507 bra isr_signed24_mult_checkA ; NO - continue checking operand A
|
|
|
508 movf isr_xA+0,W ; YES - add -16777216 * A
|
|
|
509 subwf isr_xC+3,F ; - ...
|
|
|
510 movf isr_xA+1,W ; - ...
|
|
|
511 subwfb isr_xC+4,F ; - ...
|
|
|
512 movf isr_xA+2,W ; - ...
|
|
|
513 subwfb isr_xC+5,F ; - ...
|
|
|
514 isr_signed24_mult_checkA: ; manage sign extension of operand B
|
|
|
515 btfss isr_xA+2,7 ; is A negative ?
|
|
|
516 return ; NO - done
|
|
|
517 movf isr_xB+0,W ; YES - add -16777216 * B
|
|
|
518 subwf isr_xC+3,F ; - ...
|
|
|
519 movf isr_xB+1,W ; - ...
|
|
|
520 subwfb isr_xC+4,F ; - ...
|
|
|
521 movf isr_xB+2,W ; - ...
|
|
|
522 subwfb isr_xC+5,F ; - ...
|
|
|
523 return
|
|
|
524
|
|
|
525 ;=============================================================================
|
|
|
526 math16 CODE
|
|
|
527 ;=============================================================================
|
|
|
528
|
|
|
529 ;-----------------------------------------------------------------------------
|
|
|
530 ; Divide two UNSIGNED 16 Bit Integers: isr_xC:2 = isr_xA:2 / isr_xB:2 with xA as remainder
|
|
|
531 ;
|
|
|
532 ; trashes WREG
|
|
|
533 ;
|
|
|
534 global isr_div16x16
|
|
|
535 isr_div16x16:
|
|
|
536 movlw .16 ; process 16 bits ...
|
|
|
537 movwf isr_math_loop ; ... initialize loop counter
|
|
|
538 movff isr_xA+0,isr_xC+0 ; copy isr_xA to isr_xC
|
|
|
539 movff isr_xA+1,isr_xC+1 ; ...
|
|
|
540 clrf isr_xA+0 ; clear isr_xA, will now be used to hold the remainder
|
|
|
541 clrf isr_xA+1 ; ...
|
|
|
542 isr_div16x16_1:
|
|
|
543 bcf STATUS,C ; clear carry flag to shift in a zero bit
|
|
|
544 rlcf isr_xC+0,F ; shift left isr_xC
|
|
|
545 rlcf isr_xC+1,F ; ... shifting MSB out of isr_xC...
|
|
|
546 rlcf isr_xA+0,F ; ... and into LSB of isr_xA
|
|
|
547 rlcf isr_xA+1,F ; ...
|
|
|
548 btfsc STATUS,C ; did the remainder overflow (carry set)?
|
|
|
549 bra isr_div16x16_2 ; YES - directly generate a result bit = 1
|
|
|
550 movf isr_xB+0,W ; NO - compute remainder - divisor = isr_xA - isr_xB, trash result to WREG
|
|
|
551 subwf isr_xA+0,W ; - ...
|
|
|
552 movf isr_xB+1,W ; - ...
|
|
|
553 subwfb isr_xA+1,W ; - ...
|
|
|
554 btfss STATUS,C ; - remainder < divisor (-> borrow flag set, equals carry flag cleared) ?
|
|
|
555 bra isr_div16x16_3 ; YES - result bit = 0, keep LSB of isr_xC+0 being 0
|
|
|
556 isr_div16x16_2:
|
|
|
557 bsf isr_xC+0,0 ; NO - result bit = 1, set LSB of isr_xC+0 to 1
|
|
|
558 movf isr_xB+0,W ; - subtract divisor from remainder "for real": isr_xA = isr_xA - isr_xB
|
|
|
559 subwf isr_xA+0,F ; - ...
|
|
|
560 movf isr_xB+1,W ; - ...
|
|
|
561 subwfb isr_xA+1,F ; - ...
|
|
|
562 isr_div16x16_3:
|
|
|
563 decfsz isr_math_loop,F ; decrement loop counter, all bits done?
|
|
|
564 bra isr_div16x16_1 ; NO - loop
|
|
|
565 return ; YES - done
|
|
|
566
|
|
|
567 ;=============================================================================
|
|
|
568 math17 CODE
|
|
|
569 ;=============================================================================
|
|
|
570
|
|
|
571 ;-----------------------------------------------------------------------------
|
|
|
572 ; Divide a 32 Bit Integer by a 16 Bit Integer: isr_xC:4 = isr_xC:4 / isr_xB:2 with isr_xA as remainder
|
|
|
573 ;
|
|
|
574 ; trashes WREG
|
|
|
575 ;
|
|
|
576 global isr_div32x16
|
|
|
577 isr_div32x16:
|
|
|
578 movlw .32 ; process 32 bits ...
|
|
|
579 movwf isr_math_loop ; ... initialize loop counter
|
|
|
580 clrf isr_xA+0 ; clear isr_xA, will be used to hold the remainder
|
|
|
581 clrf isr_xA+1 ; ...
|
|
|
582 isr_div32x16_1:
|
|
|
583 bcf STATUS,C ; clear carry flag to shift in a zero bit
|
|
|
584 rlcf isr_xC+0,F ; shift left isr_xC
|
|
|
585 rlcf isr_xC+1,F ; ...
|
|
|
586 rlcf isr_xC+2,F ; ...
|
|
|
587 rlcf isr_xC+3,F ; ... shifting MSB out of isr_xC...
|
|
|
588 rlcf isr_xA+0,F ; ... and into LSB of isr_xA
|
|
|
589 rlcf isr_xA+1,F ; ...
|
|
|
590 btfsc STATUS,C ; did the remainder overflow (carry set)?
|
|
|
591 bra isr_div32x16_2 ; YES - directly generate a result bit = 1
|
|
|
592 movf isr_xB+0,W ; NO - compute remainder - divisor = isr_xA - isr_xB, trash result to WREG
|
|
|
593 subwf isr_xA+0,W ; - ...
|
|
|
594 movf isr_xB+1,W ; - ...
|
|
|
595 subwfb isr_xA+1,W ; - ...
|
|
|
596 btfss STATUS,C ; - remainder < divisor (-> borrow flag set, equals carry flag cleared) ?
|
|
|
597 bra isr_div32x16_3 ; YES - result bit = 0, keep LSB of isr_xC+0 being 0
|
|
|
598 isr_div32x16_2:
|
|
|
599 bsf isr_xC+0,0 ; NO - result bit = 1, set LSB of isr_xC+0 to 1
|
|
|
600 movf isr_xB+0,W ; - subtract divisor from remainder "for real": isr_xA = isr_xA - isr_xB
|
|
|
601 subwf isr_xA+0,F ; - ...
|
|
|
602 movf isr_xB+1,W ; - ...
|
|
|
603 subwfb isr_xA+1,F ; - ...
|
|
|
604 isr_div32x16_3:
|
|
|
605 decfsz isr_math_loop,F ; decrement loop counter, all bits done?
|
|
|
606 bra isr_div32x16_1 ; NO - loop
|
|
|
607 return ; YES - done
|
|
|
608
|
|
|
609
|
|
634
|
610 ;-----------------------------------------------------------------------------
|
|
0
|
611
|
|
604
|
612 END |
