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Routines |
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Used by the routines at SetUpPiece and SetUpFlatPiece.
Finds the picture for the piece. The offset of the picture is looked up in the table that SegmentPictureOffsets points at, using the value in E as the index, and added to the address of the picture at PicturePointer. The stack pointer is pointed at the result, so that the drawing routines can pop the words of the picture. The routine then works out how many rows to draw. If the piece is at the bottom of the screen the rows that are below the bottom are skipped by popping their words.
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| LocatePicture | D672 | LD A,E | A=E. | |||||
| D673 | EXX | Switch to the alternate registers. | ||||||
| D674 | LD HL,($CE51) | Fetch the word at SegmentPictureOffsets into HL. | ||||||
| D677 | LD E,A | E=A. | ||||||
| D678 | SLA E | Shift E left. | ||||||
| D67A | LD D,$00 | Clear D. | ||||||
| D67C | ADD HL,DE | HL gains DE. | ||||||
| D67D | LD E,(HL) | Read HL into E. | ||||||
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This entry point is used by the routine at SetUpFlatPiece.
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| LocatePicture_Address | D67E | LD HL,($CE47) | Fetch the word at PicturePointer into HL. | |||||
| D681 | ADD HL,DE | HL gains DE. | ||||||
| D682 | LD SP,HL | Set the stack pointer from HL. | ||||||
| D683 | LD A,($CE40) | The segment height. | ||||||
| D686 | LD E,A | E=A. | ||||||
| D687 | LD A,($5C2D) | The segment screen row. | ||||||
| D68A | CP $B8 | Jump to AdjustPiece if A is less than B8. | ||||||
| D68C | JP C,AdjustPiece | |||||||
| D68F | SUB $B7 | Subtract B7 from A. | ||||||
| D691 | LD B,A | B=A. | ||||||
| D692 | SRL B | Shift B right. | ||||||
| D694 | LD A,E | A=E. | ||||||
| D695 | SUB B | Subtract B from A. | ||||||
| D696 | LD E,A | E=A. | ||||||
| D697 | LD A,($5C24) | The column step size. | ||||||
| D69A | LD D,A | D=A. | ||||||
| D69B | LD A,($CE37) | The vertical step. | ||||||
| D69E | AND A | Jump to LocatePicture_Skip if A is zero. | ||||||
| D69F | JR Z,LocatePicture_Skip | |||||||
| D6A1 | LD A,(IX+$00) | Read offset 00 of IX. | ||||||
| D6A4 | AND %00000111 | Keep the bits of A that are set in 07. | ||||||
| D6A6 | JR Z,LocatePicture_Skip | Jump to LocatePicture_Skip if the zero flag is set. | ||||||
| D6A8 | INC D | Advance D. | ||||||
| LocatePicture_Skip | D6A9 | LD A,D | A=D. | |||||
| LocatePicture_Pop | D6AA | POP HL | Bring HL back off the stack. | |||||
| D6AB | DEC A | Step A back. | ||||||
| D6AC | JR NZ,LocatePicture_Pop | Jump to LocatePicture_Pop if the zero flag is clear. | ||||||
| D6AE | DJNZ LocatePicture_Skip | Decrease B and jump to LocatePicture_Skip until none remain. | ||||||
| D6B0 | LD H,$57 | H=57. | ||||||
| D6B2 | LD A,($CE49) | The segment screen address. | ||||||
| D6B5 | LD L,A | L=A. | ||||||
| D6B6 | LD A,($CE36) | The column step. | ||||||
| D6B9 | ADD A,L | A gains L. | ||||||
| D6BA | AND %00011111 | Keep the bits of A that are set in 1F. | ||||||
| D6BC | OR %11000000 | Set the bits of A that are set in C0. | ||||||
| D6BE | LD L,A | L=A. | ||||||
| D6BF | LD A,($CE36) | The column step. | ||||||
| D6C2 | NEG | Negate A. | ||||||
| D6C4 | ADD A,L | A gains L. | ||||||
| D6C5 | LD L,A | L=A. | ||||||
| D6C6 | LD A,($D702) | Which drawing routine was chosen. | ||||||
| D6C9 | CP $0B | Jump to JumpToDrawingRoutine if A is not 0B. | ||||||
| D6CB | JP NZ,JumpToDrawingRoutine | |||||||
| D6CE | LD A,L | A=L. | ||||||
| D6CF | CP $DD | Jump to JumpToDrawingRoutine if A is less than DD. | ||||||
| D6D1 | JP C,JumpToDrawingRoutine | |||||||
| D6D4 | LD A,L | A=L. | ||||||
| D6D5 | SUB $20 | Subtract 20 from A. | ||||||
| D6D7 | LD L,A | L=A. | ||||||
| D6D8 | JP JumpToDrawingRoutine | Jump to JumpToDrawingRoutine. | ||||||
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