PutTile
putTile.bas
This subroutine takes a 2X2 tile of data from the given address and copies
it to the screen co-ordinates at (x, y) - x
and y
in character addresses, where 0 <= x <= 31
and
0 <= y < =23
.
Note that this uses pushes and pops to move the data, using the fastest known data moving algorithm for the Z80.
As a consequence, while active it uses ALL the registers, including alternates and IY
and IX
as well as the
Stack Pointer SP. It is kind enough to put these back for the purposes of exiting the subroutine
though - ZX BASIC uses that register quite extensively.
Also, interrupts are disabled while the copying is happening. Considering that the stack pointer is likely pointing either at the screen or the tile data, an interrupt would be disastrous. If interrupts were enabled when the SUB is called, it should re-enable them again on exit.
Note the data format is across the tile - 2 bytes for the top row, then 2 bytes for the second row...and so on until there are 2 bytes for the 16th row. Then two bytes for the top two attributes, and 2 for the bottom. It uses 36 bytes of data, starting at the address given.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 |
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Usage
Example:
Will copy a tile of data to print position 10,10 from address at label sprite.