Routines
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D564: Get Map Cell
Used by the routines at DrawView, DrawCell, DrawCellWithWalls, PlaceItems and PlaceMonsters.
Fetches the tile of a cell from Map, which is thirty-two rows of thirty-two. L is the column and H is the row. It sets CellColumn and CellRow. When bit 0 of ViewRotatedFlag is set, the map is read from the end.
Input
HL The cell: the column in L and the row in H
Output
A The tile for the cell
F The zero flag is set if the cell is empty
Work out the number of the cell.
GetMapCell D564 LD ($BBB4),HL Set CellColumn and CellRow.
D567 LD A,L Put the column in A and the row in HL.
D568 LD L,H
D569 LD H,$00
D56B ADD HL,HL Multiply the row by 20.
D56C ADD HL,HL
D56D ADD HL,HL
D56E ADD HL,HL
D56F ADD HL,HL
D570 OR L Add the column.
D571 LD L,A
Point at the map.
D572 LD BC,$5E04 Point BC at Map.
D575 LD A,($BBBA) Fetch ViewRotatedFlag.
D578 AND %00000001 Keep the lowest bit.
D57A JR Z,GetMapCell_Tile Jump to GetMapCell_Tile if the view is not rotated.
Read from the end.
D57C LD A,L Complement HL.
D57D CPL
D57E LD L,A
D57F LD A,H
D580 CPL
D581 LD H,A
D582 LD BC,$6204 Point BC past Map.
Fetch the tile.
GetMapCell_Tile D585 ADD HL,BC Add the address of the map.
D586 LD A,(HL) Fetch the tile and return.
D587 AND A
D588 RET
View the equivalent code in;
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