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Routines |
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Used by the routines at DrawingFill and DrawingLine.
Sets the pixel under the pen and paints its attribute with the ink at F60B.
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| PlotPixel | F5D2 | PUSH HL | Ask the ROM for this pixel's address and keep the mask. | |
| F5D3 | CALL PixelAddress | |||
| F5D6 | PUSH AF | |||
| F5D7 | PUSH HL | |||
| F5D8 | LD A,H | Take the high byte of the pixel address. | ||
| F5D9 | AND $18 | Keep the third of the screen it falls in. | ||
| F5DB | RRCA | Shift that third down to the low bits. | ||
| F5DC | RRCA | |||
| F5DD | RRCA | |||
| F5DE | ADD A,$58 | Add 58 to reach the attribute file. | ||
| F5E0 | LD H,A | Point at the attribute and clear its ink. | ||
| F5E1 | LD A,(HL) | |||
| F5E2 | AND $38 | |||
| F5E4 | LD (HL),A | |||
| F5E5 | LD A,($F60B) | Rotate the ink at F60B into the paper bits and skip the clash test when it already differs from the attribute. | ||
| F5E8 | RLCA | |||
| F5E9 | RLCA | |||
| F5EA | RLCA | |||
| F5EB | CP (HL) | |||
| F5EC | JR NZ,PlotPixel_0 | |||
| F5EE | XOR $38 | Flip the ink when it matches the paper colour already there, so it stays visible. | ||
| PlotPixel_0 | F5F0 | RRCA | Shift the ink back into place and merge it into the attribute. | |
| F5F1 | RRCA | |||
| F5F2 | RRCA | |||
| F5F3 | OR (HL) | |||
| F5F4 | LD (HL),A | |||
| F5F5 | POP HL | Restore the pixel address and the mask from the stack. | ||
| F5F6 | POP AF | |||
| F5F7 | OR (HL) | Set the pixel in the display byte. | ||
| F5F8 | LD (HL),A | |||
| F5F9 | POP HL | |||
| F5FA | RET | Return. | ||
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View the equivalent code in;
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