Routines
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C427: Step Up Right
Used by the routine at DrawStripsLeftToRight.
Moves the draw position up by eight pixels and right by sixteen pixels, and moves on to the next two bytes of the list of tiles.
Input
IY The address of the tile in its list
Move up and to the right, and on to the next tile.
StepUpRight C427 LD DE,$0008 Set the vertical step to eight pixels up.
Move on to the next two bytes of the list.
AdvanceListStepRight C42A INC IY Move on to the next two bytes of the list.
C42C INC IY
This entry point is used by the routine at StepUpRightKeepList.
Move the position.
StepRight C42E LD HL,($A250) Add the vertical step to ScreenVerticalPosition.
C431 ADD HL,DE
C432 LD ($A250),HL
C435 LD HL,($A24E) Move ScreenHorizontalPosition sixteen pixels to the right.
C438 LD DE,$0010
C43B ADD HL,DE
C43C LD ($A24E),HL
C43F RET Return.
This entry point is used by the routine at DrawStripsLeftToRight.
Move down and to the right, and on to the next tile.
StepDownRight C440 LD DE,$FFF8 Set the vertical step to eight pixels down.
C443 JR AdvanceListStepRight Jump to AdvanceListStepRight.
This entry point is used by the routine at DrawCellWithWalls.
Move down and to the right.
StepDownRightKeepList C445 LD DE,$FFF8 Set the vertical step to eight pixels down.
C448 JR StepRight Jump to StepRight.
This entry point is used by the routine at DrawCell.
Move up and to the left, and on to the next tile.
StepUpLeft C44A LD DE,$0008 Set the vertical step to eight pixels up.
Move on to the next two bytes of the list.
AdvanceListStepLeft C44D INC IY Move on to the next two bytes of the list.
C44F INC IY
C451 LD HL,($A250) Add the vertical step to ScreenVerticalPosition.
C454 ADD HL,DE
C455 LD ($A250),HL
C458 LD HL,($A24E) Move ScreenHorizontalPosition sixteen pixels to the left.
C45B LD DE,$FFF0
C45E ADD HL,DE
C45F LD ($A24E),HL
C462 RET Return.
This entry point is used by the routine at DrawCell.
Move down and to the left, and on to the next tile.
StepDownLeft C463 LD DE,$FFF8 Set the vertical step to eight pixels down.
C466 JR AdvanceListStepLeft Jump to AdvanceListStepLeft.
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