Routines
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DCDC: Move Tile Up
Used by the routine at F43E.
MoveTile_Up DCDC LD A,($E75E) Take *Tile_Vertical_Position and store it in A. Decrease it by one, which adjusts the value for the tile height, and write this value to *Tile_Vertical_Coordinate.
DCDF DEC A
DCE0 LD ($E760),A
DCE3 LD A,($E761) B=*Tile_SpacesToMove.
DCE6 LD B,A
MoveTile_Up_Loop DCE7 PUSH BC Stash the row counter on the stack.
DCE8 LD A,($E75D) A=*Tile_Horizontal_Position.
DCEB DEC A Decrease A by one.
DCEC LD ($E75F),A Write A to *Tile_Horizontal_Coordinate.
DCEF LD B,$04 B=04.
MoveTile_Up_0 DCF1 PUSH BC Stash the row (tile height) counter on the stack.
DCF2 LD A,($E75F) B=*Tile_Horizontal_Coordinate.
DCF5 LD B,A
DCF6 LD A,($E760) C=*Tile_Vertical_Coordinate.
DCF9 LD C,A
DCFA CALL Calculate_ScreenBlockAddress Call Calculate_ScreenBlockAddress.
DCFD PUSH HL Stash the destination screen buffer address on the stack.
DCFE DEC B Decrease B by one.
DCFF CALL Calculate_ScreenBlockAddress Call Calculate_ScreenBlockAddress.
DD02 PUSH HL DE=screen buffer address of the tile (using the stack).
DD03 POP DE
DD04 POP HL Restore the destination screen buffer address from the stack.
DD05 LD A,$08 A=08.
DD07 LD BC,$0004 BC=0004.
DD0A PUSH HL Stash HL, HL and DE on the stack.
MoveTile_Up_1 DD0B PUSH HL
DD0C PUSH DE
DD0D LDIR LDIR.
DD0F DEC HL Decrease HL by one.
DD10 PUSH HL Stash HL on the stack.
DD11 LD (HL),C Write C to *HL.
DD12 POP DE Restore DE from the stack.
DD13 DEC DE Decrease DE by one.
DD14 LD BC,$0003 BC=0003.
DD17 LDDR LDDR.
DD19 POP DE Restore DE and HL from the stack.
DD1A POP HL
DD1B INC D Increment D by one.
DD1C INC H Increment H by one.
DD1D LD BC,$0004 BC=0004.
DD20 DEC A Decrease A by one.
DD21 JP NZ,MoveTile_Up_1 Jump to MoveTile_Up_1 if A is not zero.
DD24 POP HL Restore HL from the stack.
DD25 CALL Calculate_AttributeAddress Call Calculate_AttributeAddress.
Move DE up one attribute row.
DD28 LD HL,$FFE0 DE+=FFE0 (subtract 0020).
DD2B ADD HL,DE
DD2C EX DE,HL
DD2D LD BC,$0004 BC=0004.
DD30 LDIR LDIR.
DD32 LD BC,$0003 BC=0003.
DD35 LD A,$47 A=INK: WHITE, PAPER: BLACK (BRIGHT) .
DD37 DEC HL Decrease HL by one.
DD38 LD (HL),A Write A to *HL.
DD39 PUSH HL Stash HL on the stack.
DD3A POP DE Restore DE from the stack.
DD3B DEC DE Decrease DE by one.
DD3C LDDR LDDR.
DD3E LD HL,$E75F HL=Tile_Horizontal_Coordinate.
DD41 INC (HL) Increment *HL by one.
DD42 POP BC Restore BC from the stack.
DD43 DJNZ MoveTile_Up_0 Decrease counter by one and loop back to MoveTile_Up_0 until counter is zero.
The tile has successfully moved one space!
DD45 POP BC Using the number of spaces left to move (from the stack) call Sound_TileMovement.
DD46 PUSH BC
DD47 CALL Sound_TileMovement
DD4A LD HL,$E75D Decrease *Tile_Horizontal_Position by one.
DD4D DEC (HL)
DD4E POP BC Restore the number of spaces left to move from the stack.
DD4F DJNZ MoveTile_Up_Loop Decrease the number of spaces counter by one and loop back to MoveTile_Up_Loop until the tile is in the destination space.
DD51 RET Return.
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