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Routines |
| Prev: D3D2 | Up: Map | Next: D672 |
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Used by the routine at SetUpPiece.
Sets up the drawing of the piece of picture for a step of a flat segment, which is three bytes wide. The jumps at DrawFlatRows_Next, DrawFlatRows_PatchSecond and DrawFlatRows_PatchThird and the instructions at E2A5 and E2AA of DrawFlatRows are changed when the piece is at the edge of the screen (the column in the bottom five bits of the screen address is 18, 19, 1C or 1D) so that only the part inside the area of the terrain is drawn. The routine then reads the shape at the end of the segment from StartShape and EndShape and finds the picture and the routine that draws it.
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| SetUpFlatPiece | D588 | XOR A | Clear A. | |||||||
| D589 | LD ($E25A),A | Draw the first word of the flat row. | ||||||||
| D58C | LD ($E25E),A | Draw the second word of the flat row. | ||||||||
| D58F | LD ($E262),A | Draw the third word of the flat row. | ||||||||
| D592 | LD A,($CE49) | The segment screen address. | ||||||||
| D595 | AND %00011111 | Keep the bits of A that are set in 1F. | ||||||||
| D597 | CP $1D | Jump to SetUpFlatPiece_Right if A is 1D. | ||||||||
| D599 | JR Z,SetUpFlatPiece_Right | |||||||||
| D59B | CP $1C | Jump to SetUpFlatPiece_Edge if A is 1C. | ||||||||
| D59D | JR Z,SetUpFlatPiece_Edge | |||||||||
| D59F | CP $18 | Jump to SetUpFlatPiece_Column if A is 18. | ||||||||
| D5A1 | JR Z,SetUpFlatPiece_Column | |||||||||
| D5A3 | CP $19 | Jump to SetUpFlatPiece_Skip if A is 19. | ||||||||
| D5A5 | JR Z,SetUpFlatPiece_Skip | |||||||||
| D5A7 | LD A,($D85D) | The edge flag. | ||||||||
| D5AA | AND A | Jump to FinishStep_Count if A is not zero. | ||||||||
| D5AB | JP NZ,FinishStep_Count | |||||||||
| D5AE | LD A,($5C22) | The segment length. | ||||||||
| D5B1 | CP C | Jump to SetUpFlatPiece_Shape if A is not C. | ||||||||
| D5B2 | JR NZ,SetUpFlatPiece_Shape | |||||||||
| D5B4 | LD A,($5C33) | The segment start shape. | ||||||||
| D5B7 | CP $10 | Jump to SetUpFlatPiece_Shape if A is not 10. | ||||||||
| D5B9 | JR NZ,SetUpFlatPiece_Shape | |||||||||
| D5BB | LD A,($CE41) | The horizontal offset. | ||||||||
| D5BE | AND %00000111 | Keep the bits of A that are set in 07. | ||||||||
| D5C0 | JR Z,SetUpFlatPiece_Shape | Jump to SetUpFlatPiece_Shape if the zero flag is set. | ||||||||
| D5C2 | LD A,$EE | A=EE. | ||||||||
| D5C4 | JR SetUpFlatPiece_Patch | Jump to SetUpFlatPiece_Patch. | ||||||||
| SetUpFlatPiece_Right | D5C6 | LD A,$33 | A=33. | |||||||
| SetUpFlatPiece_Patch | D5C8 | LD ($E25A),A | Skip part of the flat row at the right edge. | |||||||
| D5CB | XOR A | Clear A. | ||||||||
| D5CC | LD ($E2AA),A | Draw the right-hand byte. | ||||||||
| D5CF | INC A | Advance A. | ||||||||
| D5D0 | LD ($E2A5),A | Skip the byte before the right-hand byte. | ||||||||
| D5D3 | JR SetUpFlatPiece_Shape | Jump to SetUpFlatPiece_Shape. | ||||||||
| SetUpFlatPiece_Edge | D5D5 | LD A,$33 | A=33. | |||||||
| D5D7 | LD ($E25A),A | Skip part of the flat row at the edge. | ||||||||
| D5DA | LD A,$0B | A=0B. | ||||||||
| D5DC | LD ($E2AA),A | Skip most of the right-hand side. | ||||||||
| D5DF | XOR A | Clear A. | ||||||||
| D5E0 | LD ($E2A5),A | Draw the byte before the right-hand byte. | ||||||||
| D5E3 | JR SetUpFlatPiece_Shape | Jump to SetUpFlatPiece_Shape. | ||||||||
| SetUpFlatPiece_Column | D5E5 | LD A,$26 | A=26. | |||||||
| D5E7 | LD ($E262),A | Skip the third word of the flat row. | ||||||||
| D5EA | JR SetUpFlatPiece_Shape | Jump to SetUpFlatPiece_Shape. | ||||||||
| SetUpFlatPiece_Skip | D5EC | LD A,$24 | A=24. | |||||||
| D5EE | LD ($E25E),A | Skip the second word of the flat row. | ||||||||
| SetUpFlatPiece_Shape | D5F1 | LD A,($5C22) | The segment length. | |||||||
| D5F4 | CP C | Jump to SetUpFlatPiece_Last if A is not C. | ||||||||
| D5F5 | JP NZ,SetUpFlatPiece_Last | |||||||||
| D5F8 | LD A,($5C33) | The segment start shape. | ||||||||
| D5FB | BIT 4,A | Jump to LocatePicture if bit 4 of A is clear. | ||||||||
| D5FD | JP Z,LocatePicture | |||||||||
| D600 | OR %10000000 | Set the bits of A that are set in 80. | ||||||||
| D602 | LD ($5C33),A | Update the segment start shape. | ||||||||
| SetUpFlatPiece_Picture | D605 | LD B,A | B=A. | |||||||
| D606 | CP $96 | Jump to SetUpFlatPiece_Edges if A is 96. | ||||||||
| D608 | JR Z,SetUpFlatPiece_Edges | |||||||||
| D60A | BIT 0,A | Jump to SetUpFlatPiece_Offset if bit 0 of A is clear. | ||||||||
| D60C | JR Z,SetUpFlatPiece_Offset | |||||||||
| D60E | CP $91 | Compare A with 91. | ||||||||
| D610 | LD A,($CCBB) | The horizontal scroll speed. | ||||||||
| D613 | JR Z,SetUpFlatPiece_Direction | Jump to SetUpFlatPiece_Direction if the zero flag is set. | ||||||||
| D615 | NEG | Negate A. | ||||||||
| SetUpFlatPiece_Direction | D617 | BIT 7,A | Jump to SetUpFlatPiece_Offset if bit 7 of A is set. | |||||||
| D619 | JR NZ,SetUpFlatPiece_Offset | |||||||||
| D61B | LD A,(IX+$00) | Read offset 00 of IX. | ||||||||
| D61E | AND %00000111 | Keep the bits of A that are set in 07. | ||||||||
| D620 | JR NZ,SetUpFlatPiece_Offset | Jump to SetUpFlatPiece_Offset if the zero flag is clear. | ||||||||
| D622 | LD A,B | A=B. | ||||||||
| D623 | LD ($5C27),A | Update the shape flag. | ||||||||
| D626 | EXX | Switch to the alternate registers. | ||||||||
| D627 | LD HL,($CE49) | Fetch the word at SegmentScreenAddress into HL. | ||||||||
| D62A | LD ($CE4F),HL | Update the saved screen address. | ||||||||
| D62D | LD A,($5C2C) | The segment screen column. | ||||||||
| D630 | LD ($5C1C),A | Update the screen column. | ||||||||
| D633 | EXX | Switch to the alternate registers. | ||||||||
| D634 | JR SetUpFlatPiece_Offset | Jump to SetUpFlatPiece_Offset. | ||||||||
| SetUpFlatPiece_Edges | D636 | LD A,($CE49) | The segment screen address. | |||||||
| D639 | INC A | Advance A. | ||||||||
| D63A | INC A | Advance A. | ||||||||
| D63B | AND %00011111 | Keep the bits of A that are set in 1F. | ||||||||
| D63D | CP $1C | Jump to FinishStep_Next if A is 1C or more. | ||||||||
| D63F | JP NC,FinishStep_Next | |||||||||
| D642 | XOR A | Clear A. | ||||||||
| D643 | LD ($E25A),A | Draw the first word of the flat row. | ||||||||
| D646 | LD ($E262),A | Draw the third word of the flat row. | ||||||||
| D649 | LD A,$24 | A=24. | ||||||||
| D64B | LD ($E25E),A | Skip the second word of the flat row. | ||||||||
| SetUpFlatPiece_Offset | D64E | LD A,B | A=B. | |||||||
| D64F | AND %00000011 | Keep the bits of A that are set in 03. | ||||||||
| D651 | ADD A,A | Double A. | ||||||||
| D652 | ADD A,A | Double A. | ||||||||
| D653 | LD B,A | B=A. | ||||||||
| D654 | ADD A,A | Double A. | ||||||||
| D655 | ADD A,B | A gains B. | ||||||||
| D656 | ADD A,$24 | Add 24 to A. | ||||||||
| D658 | EXX | Switch to the alternate registers. | ||||||||
| D659 | LD E,A | E=A. | ||||||||
| D65A | LD D,$00 | Clear D. | ||||||||
| D65C | JR LocatePicture_Address | Jump to LocatePicture_Address. | ||||||||
| SetUpFlatPiece_Last | D65E | LD A,C | A=C. | |||||||
| D65F | CP $01 | Jump to LocatePicture if A is not 01. | ||||||||
| D661 | JR NZ,LocatePicture | |||||||||
| D663 | LD A,($5C34) | The segment end shape. | ||||||||
| D666 | BIT 4,A | Jump to LocatePicture if bit 4 of A is clear. | ||||||||
| D668 | JR Z,LocatePicture | |||||||||
| D66A | OR %10000000 | Set the bits of A that are set in 80. | ||||||||
| D66C | LD ($5C34),A | Update the segment end shape. | ||||||||
| D66F | JP SetUpFlatPiece_Picture | Jump to SetUpFlatPiece_Picture. | ||||||||
| Prev: D3D2 | Up: Map | Next: D672 |