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Routines |
| Prev: FEA3 | Up: Map | Next: FEF4 |
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This is the input routine for Sinclair joysticks. The Sinclair interface maps Up/Down/Left/Right/Fire to keys 9/8/6/7/0.
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| inputroutine_sinclair | FECD | LD BC,$EFFE | Load BC with the port number of the keyboard half row for keys 6/7/8/9/0 | |||||
| FED0 | IN A,(C) | Read that port. We'll receive xxx67890 | ||||||
| FED2 | CPL | The keyboard is active low, so complement the value | ||||||
| FED3 | LD BC,$0000 | Clear our left_right and up_down variables | ||||||
| FED6 | RRCA | Rotate '0' out: 0xxx6789 | ||||||
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Up
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| FED7 | RRCA | Rotate '9' out: 90xxx678 | ||||||
| FED8 | JR NC,inputroutine_sinclair_0 | If carry was set then '9' was pressed, otherwise skip | ||||||
| FEDA | LD C,$01 | up_down = input_UP | ||||||
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Down
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| inputroutine_sinclair_0 | FEDC | RRCA | Rotate '8' out: 890xxx67 | |||||
| FEDD | JR NC,inputroutine_sinclair_1 | If carry was set then '8' was pressed, otherwise skip | ||||||
| FEDF | LD C,$02 | up_down = input_DOWN | ||||||
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Right
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| inputroutine_sinclair_1 | FEE1 | RRCA | Rotate '7' out: 7890xxx6 | |||||
| FEE2 | JR NC,inputroutine_sinclair_2 | If carry was set then '7' was pressed, otherwise skip | ||||||
| FEE4 | LD B,$06 | left_right = input_RIGHT | ||||||
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Left
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| inputroutine_sinclair_2 | FEE6 | RRCA | Rotate '6' out: 67890xxx | |||||
| FEE7 | JR NC,inputroutine_sinclair_3 | If carry was set then '6' was pressed, otherwise skip | ||||||
| FEE9 | LD B,$03 | left_right = input_LEFT | ||||||
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Fire
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| inputroutine_sinclair_3 | FEEB | AND $08 | Is '0' pressed? | |||||
| FEED | JR Z,inputroutine_sinclair_4 | Jump forward if not | ||||||
| FEEF | LD A,$09 | fire = input_FIRE | ||||||
| inputroutine_sinclair_4 | FEF1 | ADD A,B | Combine the fire, up_down and left_right values | |||||
| FEF2 | ADD A,C | |||||||
| FEF3 | RET | Return | ||||||
| Prev: FEA3 | Up: Map | Next: FEF4 |