Routines
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A86E: Convert Draw Coordinate
Used by the routines at WriteSpriteBuffer and DrawRoom.
Clone of ConvertCoordinateToBufferOffset used while drawing a room. Writes the offset to BufferPointer.
Input
B Vertical position
C Horizontal position
Output
HL Buffer offset (also written to BufferPointer)
ConvertDrawCoordinate A86E LD A,$18 DE=(18-B)*20.
A870 SUB B
A871 LD E,A
A872 LD D,$00
A874 SLA E
A876 RL D
A878 SLA E
A87A RL D
A87C SLA E
A87E RL D
A880 SLA E
A882 RL D
A884 SLA E
A886 RL D
A888 LD A,$21 HL=21-C.
A88A SUB C
A88B LD L,A
A88C LD H,$00
A88E ADD HL,DE HL+=DE.
A88F LD ($BAD5),HL Write HL to *BufferPointer.
A892 RET Return.
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