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Routines |
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Used by the routine at 35090.
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| 36147 | CALL 36203 | Fill the buffer at 24064 with attribute bytes for the current room | ||
| 36150 | LD IX,24064 | Point IX at the first byte of the attribute buffer at 24064 | ||
| 36154 | LD A,112 | Set the operand of the 'LD D,n' instruction at 36188 (below) to 112 | ||
| 36156 | LD (36189),A | |||
| 36159 | CALL 36171 | Draw the tiles for the top half of the room to the screen buffer at 28672 | ||
| 36162 | LD IX,24320 | Point IX at the 256th byte of the attribute buffer at 24064 in preparation for drawing the bottom half of the room; this instruction is redundant, since IX already holds 24320 | ||
| 36166 | LD A,120 | Set the operand of the 'LD D,n' instruction at 36188 (below) to 120 | ||
| 36168 | LD (36189),A | |||
| 36171 | LD C,0 | C will count 256 tiles | ||
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The following loop draws 256 tiles (for either the top half or the bottom half of the room) to the screen buffer at 28672.
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| 36173 | LD E,C | E holds the LSB of the screen buffer address | ||
| 36174 | LD A,(IX+0) | Pick up an attribute byte from the buffer at 24064; this identifies the type of tile (background, floor, wall, nasty, ramp or conveyor) to be drawn | ||
| 36177 | LD HL,32928 | Move HL through the attribute bytes and graphic data of the background, floor, wall, nasty, ramp and conveyor tiles starting at 32928 until we find a byte that matches the attribute byte of the tile to be drawn; note that if a graphic data byte matches the attribute byte being searched for, the CPIR instruction can exit early, which is a bug | ||
| 36180 | LD BC,54 | |||
| 36183 | CPIR | |||
| 36185 | LD C,E | Restore the value of the tile counter in C | ||
| 36186 | LD B,8 | There are eight bytes in the tile | ||
| 36188 | LD D,0 | This instruction is set to either 'LD D,112' or 'LD D,120' above; now DE holds the appropriate address in the screen buffer at 28672 | ||
| 36190 | LD A,(HL) | Copy the tile graphic data to the screen buffer at 28672 | ||
| 36191 | LD (DE),A | |||
| 36192 | INC HL | |||
| 36193 | INC D | |||
| 36194 | DJNZ 36190 | |||
| 36196 | INC IX | Move IX along to the next byte in the attribute buffer | ||
| 36198 | INC C | Have we drawn 256 tiles yet? | ||
| 36199 | JP NZ,36173 | If not, jump back to draw the next one | ||
| 36202 | RET | |||
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