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1145
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1 **************************************************
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2 * System Call: F$Find64
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3 *
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4 * Function: Find a 64 byte memory block
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5 *
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6 * Input: X = Address of page table
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7 * A = Block number
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8 *
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9 * Output: Y = Address of block
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10 *
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11 * Error: CC = C bit set; B = error code
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12 *
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13 FFind64 ldx R$X,u Get block tbl ptr
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14 lda R$A,u get path block #
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15 * Find a empty path block
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16 beq L0A70 None, return error
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17 clrb calculate address
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18 IFNE H6309
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19 lsrd (Divide by 4)
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20 lsrd
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21 ELSE
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22 lsra
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23 rorb
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24 lsra
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25 rorb
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26 ENDC
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27 lda a,x is that block allocated?
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28 tfr d,x Move addr to X
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29 beq L0A70 no, return error
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30 tst ,x this the page table?
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31 bne L0A71 no, we can use this one
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32 L0A70 coma set carry & return
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33 rts
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34 L0A71 stx R$Y,u save address of block
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35 rts return
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36
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37
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38 **************************************************
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39 * System Call: F$All64
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40 *
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41 * Function: Allocate a 64 byte memory block
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42 *
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43 * Input: X = Address of page table (0 if page table hasn't been allocated)
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44 *
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45 * Output: A = Block number
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46 * X = Address of page table
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47 * Y = Address of block
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48 *
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49 * Error: CC = C bit set; B = error code
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50 *
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51 *
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52 FAll64 ldx R$X,u get base address of page table
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53 bne L0A7F it's been allocated, skip ahead
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54 bsr L0A89 allocate the page
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55 bcs L0A88 error allocating, return
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56 stx ,x save base address in page table
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57 stx R$X,u save base address to caller's X
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58 L0A7F bsr L0A9F find a empty spot in path table
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59 bcs L0A88 couldn't find one, return error
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60 sta R$A,u save block #
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61 sty R$Y,u save address of block
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62 L0A88 rts return
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63
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64 * Allocate a new base page
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65 * Exit: X=Ptr to newly allocated 256 byte page
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66 L0A89 pshs u preserve register stack pointer
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67 IFNE H6309
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68 ldq #$01000100 get block size (1 for SRqMem & 1 for TFM)
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69 ELSE
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70 ldd #$0100
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71 ENDC
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72 os9 F$SRqMem request mem for it
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73 leax ,u point to it
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74 ldu ,s restore register stack pointer
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75 stx ,s save pointer to new page on stack
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76 bcs L0A9E error on allocate, return
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77 * Clear freshly allocated page to 0's
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78 IFNE H6309
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79 leay TFMNull,pc point to NULL byte
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80 tfm y,x+
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81 ELSE
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82 clrb
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83 AllLoop clr ,x+
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84 decb
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85 bne AllLoop
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86 ENDC
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87 L0A9E puls x,pc
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88
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89 IFNE H6309
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90 TFMNull fcb 0 used to clear memory
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91 ENDC
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92
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93 * Search page table for a free 64 byte block
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94 * Entry: X=Ptr to base page (the one with the 64 entry page index)
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95 L0A9F pshs x,u preserve base page & register stack ptrs
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96 clra Index entry #=0
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97 * Main search loop
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98 L0AA2 pshs a Save which index entry we are checking
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99 clrb Set position within page we are checking to 0
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100 lda a,x Is the current index entry used?
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101 beq L0AB4 no, skip ahead
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102 tfr d,y Yes, Move ptr to 256 byte block to Y
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103 clra Clear offset for 64 byte blocks to 0
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104 L0AAC tst d,y Is this 64 byte block allocated?
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105 beq L0AB6 No, skip ahead
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106 addb #$40 Yes, point to next 64 byte block in page
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107 bcc L0AAC If not done checking entire page, keep going
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108
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109 * Index entry has a totally unused 256 byte page
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110 L0AB4 orcc #Carry Set flag (didn't find one)
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111 L0AB6 leay d,y
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112 puls a Get which index entry we were checking
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113 bcc L0AE1 If we found a blank entry, go allocate it
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114 inca Didn't, move to next index entry
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115 cmpa #64 Done entire index?
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116 blo L0AA2 no, keep looking
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117
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118 clra Yes, clear out to first entry
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119 L0AC2 tst a,x Is this one used?
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120 beq L0AD0 No, skip ahead
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121 inca Increment index entry #
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122 cmpa #64 Done entire index?
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123 blo L0AC2 No, continue looking
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124
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125 comb Done all of them, exit with Path table full error
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126 ldb #E$PthFul
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127 puls x,u,pc
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128 * Found empty page
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129 L0AD0 pshs x,a Preserve index ptr & index entry #
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130 bsr L0A89 Allocate & clear out new 256 byte page
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131 bcs L0AF0 If error,exit
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132 leay ,x Point Y to start of new page
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133 tfr x,d Also copy to D
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134 tfr a,b Page # into B
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135 puls x,a Get back index ptr & index entry #
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136 stb a,x Save page # in proper index entry
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137 clrb D=index entry #*256
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138
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139 * D = Block Address
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140 L0AE1 equ *
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141 IFNE H6309
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142 lsld ???Calculate 256 byte page #?
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143 lsld
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1239
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144 tfr y,u U=Ptr to start of new page
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145 ldw #$3f Clear out the 64 byte block we are using
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146 leax TFMNull,pc
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147 tfm x,u+
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1145
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148 ELSE
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149 aslb
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150 rola
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151 aslb
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152 rola
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153 ldb #$3f
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1239
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154 ClrIt clr b,y
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1145
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155 decb
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156 bne ClrIt
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157 ENDC
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158 sta ,y Save 256 byte page # as 1st byte of block
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159 puls x,u,pc
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160
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161 L0AF0 leas 3,s
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162 puls x,u,pc
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163
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164
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165 **************************************************
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166 * System Call: F$Ret64
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167 *
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168 * Function: Deallocate a 64 byte memory block
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169 *
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170 * Input: X = Address of page table
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171 * A = Block number
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172 *
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173 * Output: None
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174 *
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175 * Error: CC = C bit set; B = error code
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176 *
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177 FRet64 lda R$A,u
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178 ldx R$X,u
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179 pshs u,y,x,d
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180 clrb
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181 tsta
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182 beq L0B22
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183 IFNE H6309
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184 lsrd (Divide by 4)
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185 lsrd
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186 ELSE
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187 lsra
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188 rorb
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189 lsra
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190 rorb
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191 ENDC
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192 pshs a
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193 lda a,x
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194 beq L0B20
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195 tfr d,y
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196 clr ,y
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197 clrb
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198 tfr d,u
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199 clra
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200 L0B10 tst d,u
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201 bne L0B20
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202 addb #$40
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203 bne L0B10
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204 inca
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205 os9 F$SRtMem
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206 lda ,s
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207 clr a,x
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208 L0B20 clr ,s+
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209 L0B22 puls pc,u,y,x,d
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