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1706
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1 *****************************************************************************
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2 * *
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3 * SUBS for st picture format *
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4 * *
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5 * STshowpic -- Displays picture, using putline routine *
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6 * *
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7 *****************************************************************************
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8
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9 check macro
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10 pshs b,cc
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11 ldb #\1
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12 os9 F$PErr
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13 puls b,cc
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14 endm
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15
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16 ifp1
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1777
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17 use os9defs.a
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1706
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18 endc
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19
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20 psect view_st_a,0,0,0,0,0
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21
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22 vsect dp
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23 linesize rmb 2 Bytes per line.
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24 totlines rmb 2 total lines in picture.
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25 curline rmb 2 Number of current screen line.
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26 fitcount rmb 2 Used to decide what lines to skip.
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27 linesleft rmb 2 Lines left in picture.
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28 endsect
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29
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30 STshowpic:
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31 bsr header Get header info
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32
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33 ldd <Skiplines
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34 beq skip01
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35 skip00
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36 lbsr getline
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37 subd #1
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38 bne skip00
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39 skip01
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40
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41 spscreens
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42 lbsr getline
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43
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44 tst <endoffile
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45 bne showpicend
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46 lbsr setscreen Set up screen
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47 lbsr setpals Set up palettes
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48 lbsr setbuffer Set up Get/Put Buffer
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49
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50 ldd #00
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51 std curline
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52 showpicloop
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53 lbsr putline
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54 ldd fitcount
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55 addd totlines
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56 spget
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57 std fitcount
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58 lbsr getline
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59 tst <Size
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60 bne spnofit
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61 ldd fitcount
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62 subd #192
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63 bge spget
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64 std fitcount
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65 spnofit
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66 ldd curline
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67 addd #1
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68 std curline
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69 cmpd #192
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70 bne showpicloop
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71 ldd linesleft
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72 cmpd #16
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73 bhi spscreens
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74 showpicend
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75 rts
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76
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77 *
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78 * read header info from file, and set window type information
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79 *
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80 vsect dp
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81 endoffile rmb 1
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82 endsect
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83
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84 header
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85 pshs a,b,x,y,u
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86 leax altbuff,y read in type and palettes into altbuff
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87 pshs y
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88 ldy #34
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89 lbsr I_Read
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90 lbcs _error
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91 puls y
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92 leax altbuff,y
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93 lda ,x+
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94
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95 lda ,x+ This byte is the screen type.
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96
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97 bne head0
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98 lda #8
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99 sta <type
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100 ldd #200
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101 std totlines
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102 std linesleft
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103 ldd #160
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104 std linesize
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105 bra headpals
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106 head0
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107
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108 cmpa #1
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109 bne head1
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110 lda #7
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111 sta <type
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112 ldd #200
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113 std totlines
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114 std linesleft
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115 ldd #160
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116 std linesize
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117 bra headpals
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118 head1
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119
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120 cmpa #2
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121 bne head2
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122 lda #5 640 2-color screen.
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123 sta <type
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124 ldd #400
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125 std totlines
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126 std linesleft
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127 ldd #80
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128 std linesize
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129 bra headpals
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130 head2
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131
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132 headpals
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133 leau palette,y Need to expand palettes out to 3 bytes/palette
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134 ldb #16 16 palettes to expand out.
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135 headexp
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136 lda ,x+
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137 anda #$0f Red is in lower nybble of first byte.
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138 sta ,u+
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139 lda ,x Second byte is: upper nybble green, lower nybble blue.
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140 lsra
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141 lsra
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142 lsra
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143 lsra
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144 sta ,u+
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145 lda ,x+
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146 anda #$0f
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147 sta ,u+
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148 decb
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149 bne headexp
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150
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151 lbsr palscale First, scale so largest is 255
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152 lbsr palconv Convert palette values from ST to CoCo format
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153
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154 * Set some miscellaneous variables
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155 lda <cyclestart No cycling
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156 sta <cycleend
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157 clr <extranum No color rotation
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158
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159 ldd <Skiplines
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160 cmpd #$ffff Is Skiplines still default?
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161 bne headskip No, don't change it.
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162 ldd #0
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163 std <Skiplines Set it to 0
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164 headskip
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165
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166 lda <Size
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167 bpl headsize Default size is BIG
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168 lda #1
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169 sta <Size
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170 headsize
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171
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172 puls a,b,x,y,u,pc
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173
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174 *
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175 * Getline
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176 *
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177 getline
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178 pshs a,b,x,y,u
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179 * First, fill buffers with all zeros
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180 leau linebuff,y
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181 leax altbuff,y
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182 ldb #160
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183 getline3
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184 clr ,u+
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185 clr ,x+
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186 decb
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187 bne getline3
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188 * If at end of file, leave it that way
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189 tst endoffile
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190 beq getline5
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191 ldd #0
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192 std linesleft First, set number of lines remaining to zero.
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193 lbra getline1
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194 getline5
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195 * Count down lines left
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196 ldd linesleft
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197 bne getline6
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198 com endoffile If no lines left, force end of file condition.
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199 lbra getline1
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200 getline6
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201 subd #1
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202 std linesleft
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203 * Get a line from the file
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204 leax altbuff,y read in one line of screen
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205 pshs y
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206 ldy <linesize Warning: Mung Y!
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207 lbsr I_Read
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208 puls y
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209 lbcs geteof Error through EOF check.
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210 * Now, we have to interleave the bits to get CoCo screen format.
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211 leax altbuff,y
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212 leau linebuff,y
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213 ldy <linesize Total number of bytes to convert.
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214 lda <type
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215
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216 cmpa #5
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217 bne conv5
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218 cnv5loop
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219 lda ,x+ This type screen, just copy the data.
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220 sta ,u+
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221 leay -1,y
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222 bne cnv5loop
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223 lbra getline1
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224 conv5
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225
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226 cmpa #7 Type 7 screen requires 2-way interleaving.
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227 bne conv7
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228 cnv7loop
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229 lbsr twolev
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230 leax 1,x
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231 lbsr twolev
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232 leax 3,x
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233 leay -4,y
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234 bne cnv7loop
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235 lbra getline1 Now we're done.
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236 conv7
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237
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238 cmpa #8 Type 8 screen requires 4-way interleaving.
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239 bne conv8
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240 cnv8loop
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241 lbsr fourlev Convert 4 bytes out of 8 -- X-X-X-X-
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242 leax 1,x Offset to next 4
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243 lbsr fourlev Convert 4 bytes out of 8 -- -X-X-X-X
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244 leax 7,x Now, skip to next 8.
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245 leay -8,y Count down number of bytes.
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246 bne cnv8loop
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247 bra getline1 Now exit.
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248 conv8
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249 bra getline1 Now exit.
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250
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251 geteof
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252 cmpb #E$EOF
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253 bne getline4
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254 com endoffile
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255 bra getline1
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256 getline4
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257 lbra _error If not EOF, just exit with error.
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258 getline1
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259 puls a,b,x,y,u,pc
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260
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261 * converts bytes 0,x 2,x 4,x and 6,x into 4 CoCo-format bytes
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262 * at [u]. U is advanced by 4, other regs unchanged.
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263
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264 fourtab
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265 fdb $0000,$0001,$0010,$0011,$0100,$0101,$0110,$0111
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266 fdb $1000,$1001,$1010,$1011,$1100,$1101,$1110,$1111
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267
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268 fourlev
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269 pshs a,b,x,y
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270 leay fourtab,pcr
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271 ldb #4
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272 pshs b 4 bytes to worry about.
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273 bra fourlev1
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274 fourlev0
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275 lsl 3,u
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276 rol 2,u
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277 rol 1,u
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278 rol ,u
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279 fourlev1
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280 lda ,x Get high nybble of byte.
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281 lsra
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282 lsra
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283 lsra
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284 anda #$1e
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285 ldd a,y Expand it out.
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286 ora ,u Or it into stuff so far.
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287 orb 1,u
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288 std ,u
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289 lda ,x++ Get low nybble, and advance to next byte.
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290 anda #$0f
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291 lsla
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292 ldd a,y Expand it out.
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293 ora 2,u Or into stuff so far.
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294 orb 3,u
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295 std 2,u
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296 dec ,s Have we done all four bytes?
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297 bne fourlev0
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298 puls b Clean up stack.
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299 leau 4,u
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300 puls a,b,x,y,pc
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301
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302 twolev
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303 bsr twolev1
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304 twolev1
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305 pshs a,b
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306 ldb #4
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307 twoloop
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308 lsl ,x
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309 rola
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310 lsl 2,x
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311 rola
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312 decb
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313 bne twoloop
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314 sta ,u+
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315 puls a,b,pc
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316
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317
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318 endsect
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