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Routines |
| Prev: A59F | Up: Map | Next: A669 |
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Erases one row of a sprite that is aligned to a byte from the screen. The entry point depends on the width of the sprite in bytes, from six bytes at EraseAlignedRowDirectly to one byte at EraseAlignedRowDirectly_Sixth. Each byte clears the pixels of the screen that are set in the sprite.
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| EraseAlignedRowDirectly | A629 | LD A,(DE) | Fetch a byte of the sprite. | |||||||
| A62A | CPL | Invert it. | ||||||||
| A62B | AND (HL) | Clear the pixels of the screen. | ||||||||
| A62C | LD (HL),A | Store the byte. | ||||||||
| A62D | INC L | Move on to the next byte of the screen. | ||||||||
| A62E | INC DE | Move on to the next byte of the sprite. | ||||||||
| EraseAlignedRowDirectly_Second | A62F | LD A,(DE) | Fetch a byte of the sprite. | |||||||
| A630 | CPL | Invert it. | ||||||||
| A631 | AND (HL) | Clear the pixels of the screen. | ||||||||
| A632 | LD (HL),A | Store the byte. | ||||||||
| A633 | INC L | Move on to the next byte of the screen. | ||||||||
| A634 | INC DE | Move on to the next byte of the sprite. | ||||||||
| EraseAlignedRowDirectly_Third | A635 | LD A,(DE) | Fetch a byte of the sprite. | |||||||
| A636 | CPL | Invert it. | ||||||||
| A637 | AND (HL) | Clear the pixels of the screen. | ||||||||
| A638 | LD (HL),A | Store the byte. | ||||||||
| A639 | INC L | Move on to the next byte of the screen. | ||||||||
| A63A | INC DE | Move on to the next byte of the sprite. | ||||||||
| EraseAlignedRowDirectly_Fourth | A63B | LD A,(DE) | Fetch a byte of the sprite. | |||||||
| A63C | CPL | Invert it. | ||||||||
| A63D | AND (HL) | Clear the pixels of the screen. | ||||||||
| A63E | LD (HL),A | Store the byte. | ||||||||
| A63F | INC L | Move on to the next byte of the screen. | ||||||||
| A640 | INC DE | Move on to the next byte of the sprite. | ||||||||
| EraseAlignedRowDirectly_Fifth | A641 | LD A,(DE) | Fetch a byte of the sprite. | |||||||
| A642 | CPL | Invert it. | ||||||||
| A643 | AND (HL) | Clear the pixels of the screen. | ||||||||
| A644 | LD (HL),A | Store the byte. | ||||||||
| A645 | INC L | Move on to the next byte of the screen. | ||||||||
| A646 | INC DE | Move on to the next byte of the sprite. | ||||||||
| EraseAlignedRowDirectly_Sixth | A647 | LD A,(DE) | Fetch a byte of the sprite. | |||||||
| A648 | CPL | Invert it. | ||||||||
| A649 | AND (HL) | Clear the pixels of the screen. | ||||||||
| A64A | LD (HL),A | Store the byte. | ||||||||
| A64B | INC DE | Move on to the next byte of the sprite. | ||||||||
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This entry point is used by the routine at EraseMirroredRowDirectly.
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| EraseAlignedRowDirectly_Next | A64C | LD A,($5C28) | Fetch the low byte of the screen address of the start of the row. | |||||||
| A64F | LD L,A | Restore it. | ||||||||
| A650 | DEC H | Move up a pixel row. | ||||||||
| A651 | LD A,H | Fetch the high byte. | ||||||||
| A652 | INC A | Add one. | ||||||||
| A653 | AND %00000111 | Keep the bits that give the pixel row. | ||||||||
| A655 | JP NZ,DrawNextRow | Jump to DrawNextRow if the row is still in the same cell. | ||||||||
| A658 | LD A,L | Fetch the low byte. | ||||||||
| A659 | SUB $20 | Move up a row of cells. | ||||||||
| A65B | LD L,A | Store it. | ||||||||
| A65C | LD ($5C28),A | Store it as the start of the row. | ||||||||
| A65F | JP C,DrawNextRow | Jump to DrawNextRow if that crossed a third of the screen. | ||||||||
| A662 | LD A,H | Fetch the high byte. | ||||||||
| A663 | ADD A,$08 | Add eight to correct it. | ||||||||
| A665 | LD H,A | Store it. | ||||||||
| A666 | JP DrawNextRow | Jump to DrawNextRow. | ||||||||
| Prev: A59F | Up: Map | Next: A669 |