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Routines |
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Used by the routines at DrawingFill and DrawingLine.
Moves the pen one pixel up the screen. E counts up from the bottom row, because PixelAddress hands it to the ROM PIXEL-ADD routine. When the pen would pass the top row (E=176) it stays put and the zero flag is set.
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| StepPenUp | 62794 | INC E | Move the pen up and return when it is still on screen. | |
| 62795 | LD H,A | |||
| 62796 | LD A,E | |||
| 62797 | CP 176 | |||
| 62799 | LD A,H | |||
| 62800 | RET NZ | |||
| 62801 | DEC E | The pen passed the top row, so step back and tell the caller it did not move. | ||
| 62802 | XOR A | |||
| 62803 | LD A,H | |||
| 62804 | RET | Return. | ||
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View the equivalent code in;
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