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1 .text
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2
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3 *-------------------------------------------------------
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4 *
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5 * Sega startup code for the GNU Assembler
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6 * Translated from:
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7 * Sega startup code for the Sozobon C compiler
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8 * Written by Paul W. Lee
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9 * Modified by Charles Coty
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10 * Modified by Stephane Dallongeville
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11 *
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12 *-------------------------------------------------------
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13
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14 .org 0x00000000
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15
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16 _Start_Of_Rom:
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17 _Vecteurs_68K:
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18 dc.l 0x00FFFE00 /* Stack address */
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19 dc.l _Entry_Point /* Program start address */
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20 dc.l _Bus_Error
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21 dc.l _Address_Error
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22 dc.l _Illegal_Instruction
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23 dc.l _Zero_Divide
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24 dc.l _Chk_Instruction
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25 dc.l _Trapv_Instruction
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26 dc.l _Privilege_Violation
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27 dc.l _Trace
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28 dc.l _Line_1010_Emulation
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29 dc.l _Line_1111_Emulation
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30 dc.l _Error_Exception, _Error_Exception, _Error_Exception, _Error_Exception
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31 dc.l _Error_Exception, _Error_Exception, _Error_Exception, _Error_Exception
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32 dc.l _Error_Exception, _Error_Exception, _Error_Exception, _Error_Exception
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33 dc.l _Error_Exception, _INT, _EXTINT, _INT
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34 dc.l _HINT
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35 dc.l _INT
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36 dc.l _VINT
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37 dc.l _INT
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38 dc.l _INT,_INT,_INT,_INT,_INT,_INT,_INT,_INT
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39 dc.l _INT,_INT,_INT,_INT,_INT,_INT,_INT,_INT
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40 dc.l _INT,_INT,_INT,_INT,_INT,_INT,_INT,_INT
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41 dc.l _INT,_INT,_INT,_INT,_INT,_INT,_INT,_INT
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42
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43 .incbin "boot/rom_head.bin", 0x10, 0x100
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44
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45 _Entry_Point:
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46 move #0x2700,%sr
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47 tst.l 0xa10008
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48 bne.s SkipJoyDetect
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49 tst.w 0xa1000c
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50 SkipJoyDetect:
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51 bne.s SkipSetup
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52
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53 lea Table,%a5
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54 movem.w (%a5)+,%d5-%d7
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55 movem.l (%a5)+,%a0-%a4
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56 * Check Version Number
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57 move.b -0x10ff(%a1),%d0
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58 andi.b #0x0f,%d0
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59 beq.s WrongVersion
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60 * Sega Security Code (SEGA)
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61 move.l #0x53454741,0x2f00(%a1)
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62 WrongVersion:
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63 move.w (%a4),%d0
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64 moveq #0x00,%d0
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65 movea.l %d0,%a6
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66 move %a6,%usp
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67 move.w %d7,(%a1)
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68 move.w %d7,(%a2)
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69 jmp Continue
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70
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71 Table:
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72 dc.w 0x8000,0x3fff,0x0100
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73 dc.l 0xA00000,0xA11100,0xA11200,0xC00000,0xC00004
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74
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75 SkipSetup:
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76 move.w #0,%a7
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77 jmp _reset_entry
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78
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79 Continue:
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80
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81 * clear Genesis RAM
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82 lea 0xff0000,%a0
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83 moveq #0,%d0
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84 move.w #0x3FFF,%d1
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85
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86 ClearRam:
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87 move.l %d0,(%a0)+
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88 dbra %d1,ClearRam
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89
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90 * copy initialized variables from ROM to Work RAM
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91 lea _stext,%a0
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92 lea 0xFF0000,%a1
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93 move.l #_sdata,%d0
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94 lsr.l #1,%d0
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95 beq NoCopy
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96
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97 subq.w #1,%d0
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98 CopyVar:
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99 move.w (%a0)+,(%a1)+
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100 dbra %d0,CopyVar
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101
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102 NoCopy:
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103
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104 * Jump to initialisation process...
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105
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106 move.w #0,%a7
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107 jmp _start_entry
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108
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109
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110 *------------------------------------------------
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111 *
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112 * interrupt functions
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113 *
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114 *------------------------------------------------
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115
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116 _Bus_Error:
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117 movem.l %d0-%d1/%a0-%a1,-(%sp)
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118 move.l busErrorCB, %a0
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119 jsr (%a0)
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120 movem.l (%sp)+,%d0-%d1/%a0-%a1
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121 rte
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122
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123 _Address_Error:
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124 movem.l %d0-%d1/%a0-%a1,-(%sp)
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125 move.l addressErrorCB, %a0
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126 jsr (%a0)
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127 movem.l (%sp)+,%d0-%d1/%a0-%a1
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128 rte
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129
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130 _Illegal_Instruction:
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131 movem.l %d0-%d1/%a0-%a1,-(%sp)
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132 move.l illegalInstCB, %a0
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133 jsr (%a0)
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134 movem.l (%sp)+,%d0-%d1/%a0-%a1
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135 rte
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136
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137 _Zero_Divide:
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138 movem.l %d0-%d1/%a0-%a1,-(%sp)
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139 move.l zeroDivideCB, %a0
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140 jsr (%a0)
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141 movem.l (%sp)+,%d0-%d1/%a0-%a1
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142 rte
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143
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144 _Chk_Instruction:
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145 movem.l %d0-%d1/%a0-%a1,-(%sp)
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146 move.l chkInstCB, %a0
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147 jsr (%a0)
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148 movem.l (%sp)+,%d0-%d1/%a0-%a1
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149 rte
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150
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151 _Trapv_Instruction:
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152 movem.l %d0-%d1/%a0-%a1,-(%sp)
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153 move.l trapvInstCB, %a0
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154 jsr (%a0)
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155 movem.l (%sp)+,%d0-%d1/%a0-%a1
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156 rte
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157
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158 _Privilege_Violation:
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159 movem.l %d0-%d1/%a0-%a1,-(%sp)
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160 move.l privilegeViolationCB, %a0
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161 jsr (%a0)
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162 movem.l (%sp)+,%d0-%d1/%a0-%a1
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163 rte
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164
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165 _Trace:
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166 movem.l %d0-%d1/%a0-%a1,-(%sp)
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167 move.l traceCB, %a0
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168 jsr (%a0)
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169 movem.l (%sp)+,%d0-%d1/%a0-%a1
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170 rte
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171
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172 _Line_1010_Emulation:
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173 _Line_1111_Emulation:
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174 movem.l %d0-%d1/%a0-%a1,-(%sp)
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175 move.l line1x1xCB, %a0
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176 jsr (%a0)
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177 movem.l (%sp)+,%d0-%d1/%a0-%a1
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178 rte
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179
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180 _Error_Exception:
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181 movem.l %d0-%d1/%a0-%a1,-(%sp)
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182 move.l errorExceptionCB, %a0
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183 jsr (%a0)
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184 movem.l (%sp)+,%d0-%d1/%a0-%a1
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185 rte
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186
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187 _INT:
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188 movem.l %d0-%d1/%a0-%a1,-(%sp)
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189 move.l intCB, %a0
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190 jsr (%a0)
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191 movem.l (%sp)+,%d0-%d1/%a0-%a1
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192 rte
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193
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194 _EXTINT:
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195 movem.l %d0-%d1/%a0-%a1,-(%sp)
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196 move.l internalExtIntCB, %a0
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197 jsr (%a0)
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198 movem.l (%sp)+,%d0-%d1/%a0-%a1
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199 rte
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200
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201 _HINT:
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202 movem.l %d0-%d1/%a0-%a1,-(%sp)
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203 move.l internalHIntCB, %a0
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204 jsr (%a0)
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205 movem.l (%sp)+,%d0-%d1/%a0-%a1
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206 rte
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207
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208 _VINT:
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209 movem.l %d0-%d1/%a0-%a1,-(%sp)
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210 move.l internalVIntCB, %a0
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211 jsr (%a0)
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212 movem.l (%sp)+,%d0-%d1/%a0-%a1
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213 rte
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214
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215 *------------------------------------------------
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216 *
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217 * Copyright (c) 1988 by Sozobon, Limited. Author: Johann Ruegg
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218 *
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219 * Permission is granted to anyone to use this software for any purpose
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220 * on any computer system, and to redistribute it freely, with the
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221 * following restrictions:
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222 * 1) No charge may be made other than reasonable charges for reproduction.
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223 * 2) Modified versions must be clearly marked as such.
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224 * 3) The authors are not responsible for any harmful consequences
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225 * of using this software, even if they result from defects in it.
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226 *
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227 *------------------------------------------------
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228
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229 ldiv:
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230 move.l 4(%a7),%d0
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231 bpl ld1
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232 neg.l %d0
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233 ld1:
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234 move.l 8(%a7),%d1
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235 bpl ld2
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236 neg.l %d1
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237 eor.b #0x80,4(%a7)
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238 ld2:
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239 bsr i_ldiv /* d0 = d0/d1 */
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240 tst.b 4(%a7)
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241 bpl ld3
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242 neg.l %d0
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243 ld3:
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244 rts
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245
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246 lmul:
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247 move.l 4(%a7),%d0
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248 bpl lm1
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249 neg.l %d0
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250 lm1:
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251 move.l 8(%a7),%d1
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252 bpl lm2
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253 neg.l %d1
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254 eor.b #0x80,4(%a7)
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255 lm2:
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256 bsr i_lmul /* d0 = d0*d1 */
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257 tst.b 4(%a7)
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258 bpl lm3
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259 neg.l %d0
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260 lm3:
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261 rts
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262
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263 lrem:
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264 move.l 4(%a7),%d0
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265 bpl lr1
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266 neg.l %d0
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267 lr1:
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268 move.l 8(%a7),%d1
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269 bpl lr2
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270 neg.l %d1
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271 lr2:
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272 bsr i_ldiv /* d1 = d0%d1 */
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273 move.l %d1,%d0
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274 tst.b 4(%a7)
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275 bpl lr3
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276 neg.l %d0
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277 lr3:
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278 rts
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279
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280 ldivu:
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281 move.l 4(%a7),%d0
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282 move.l 8(%a7),%d1
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283 bsr i_ldiv
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284 rts
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285
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286 lmulu:
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287 move.l 4(%a7),%d0
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288 move.l 8(%a7),%d1
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289 bsr i_lmul
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290 rts
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291
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292 lremu:
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293 move.l 4(%a7),%d0
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294 move.l 8(%a7),%d1
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295 bsr i_ldiv
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296 move.l %d1,%d0
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297 rts
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298 *
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299 * A in d0, B in d1, return A*B in d0
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300 *
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301 i_lmul:
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302 move.l %d3,%a2 /* save d3 */
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303 move.w %d1,%d2
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304 mulu %d0,%d2 /* d2 = Al * Bl */
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305
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306 move.l %d1,%d3
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307 swap %d3
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308 mulu %d0,%d3 /* d3 = Al * Bh */
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309
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310 swap %d0
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311 mulu %d1,%d0 /* d0 = Ah * Bl */
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312
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313 add.l %d3,%d0 /* d0 = (Ah*Bl + Al*Bh) */
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314 swap %d0
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315 clr.w %d0 /* d0 = (Ah*Bl + Al*Bh) << 16 */
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316
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317 add.l %d2,%d0 /* d0 = A*B */
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318 move.l %a2,%d3 /* restore d3 */
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319 rts
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320 *
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321 *A in d0, B in d1, return A/B in d0, A%B in d1
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322 *
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323 i_ldiv:
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324 tst.l %d1
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325 bne nz1
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326
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327 * divide by zero
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328 * divu #0,%d0 /* cause trap */
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329 move.l #0x80000000,%d0
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330 move.l %d0,%d1
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331 rts
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332 nz1:
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333 move.l %d3,%a2 /* save d3 */
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334 cmp.l %d1,%d0
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335 bhi norm
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336 beq is1
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337 * A<B, so ret 0, rem A
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338 move.l %d0,%d1
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339 clr.l %d0
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340 move.l %a2,%d3 /* restore d3 */
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341 rts
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342 * A==B, so ret 1, rem 0
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343 is1:
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344 moveq.l #1,%d0
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345 clr.l %d1
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346 move.l %a2,%d3 /* restore d3 */
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347 rts
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348 * A>B and B is not 0
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349 norm:
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350 cmp.l #1,%d1
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351 bne not1
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352 * B==1, so ret A, rem 0
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353 clr.l %d1
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354 move.l %a2,%d3 /* restore d3 */
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355 rts
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356 * check for A short (implies B short also)
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357 not1:
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358 cmp.l #0xffff,%d0
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359 bhi slow
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360 * A short and B short -- use 'divu'
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361 divu %d1,%d0 /* d0 = REM:ANS */
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362 swap %d0 /* d0 = ANS:REM */
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363 clr.l %d1
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364 move.w %d0,%d1 /* d1 = REM */
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365 clr.w %d0
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366 swap %d0
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367 move.l %a2,%d3 /* restore d3 */
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368 rts
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369 * check for B short
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370 slow:
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371 cmp.l #0xffff,%d1
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372 bhi slower
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373 * A long and B short -- use special stuff from gnu
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374 move.l %d0,%d2
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375 clr.w %d2
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376 swap %d2
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377 divu %d1,%d2 /* d2 = REM:ANS of Ahi/B */
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378 clr.l %d3
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379 move.w %d2,%d3 /* d3 = Ahi/B */
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380 swap %d3
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381
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382 move.w %d0,%d2 /* d2 = REM << 16 + Alo */
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383 divu %d1,%d2 /* d2 = REM:ANS of stuff/B */
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384
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385 move.l %d2,%d1
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386 clr.w %d1
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387 swap %d1 /* d1 = REM */
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388
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389 clr.l %d0
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390 move.w %d2,%d0
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391 add.l %d3,%d0 /* d0 = ANS */
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392 move.l %a2,%d3 /* restore d3 */
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393 rts
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394 * A>B, B > 1
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395 slower:
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396 move.l #1,%d2
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397 clr.l %d3
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398 moreadj:
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399 cmp.l %d0,%d1
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400 bhs adj
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401 add.l %d2,%d2
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402 add.l %d1,%d1
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403 bpl moreadj
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404 * we shifted B until its >A or sign bit set
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405 * we shifted #1 (d2) along with it
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406 adj:
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407 cmp.l %d0,%d1
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408 bhi ltuns
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409 or.l %d2,%d3
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410 sub.l %d1,%d0
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411 ltuns:
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412 lsr.l #1,%d1
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413 lsr.l #1,%d2
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414 bne adj
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415 * d3=answer, d0=rem
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416 move.l %d0,%d1
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417 move.l %d3,%d0
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418 move.l %a2,%d3 /* restore d3 */
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419 rts
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420
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