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Routines |
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Used by the routine at MainMenu.
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Read from the keyboard- returns 0 when no keys are being pressed.
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| Debounce_CheckKeys | 38099 | CALL 38495 | Call 38495. | |
| 38102 | OR A | Jump back to Debounce_CheckKeys if any keys are still being pressed. | ||
| 38103 | JR NZ,Debounce_CheckKeys | |||
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After the frame delay, return regardless of key presses.
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| 38105 | LD B,50 | Set a timeout counter in B of 50. | ||
| Debounce_Loop | 38107 | HALT | Halt operation (suspend CPU until the next interrupt). | |
| 38108 | XOR A | Reset the flags. | ||
| 38109 | IN A,(254) | Read from the keyboard port. | ||
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Mask off the unused bits.
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| 38111 | OR %11100000 | Set bits 5-7. | ||
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If no keys are being pressed, A will become 0.
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| 38113 | INC A | Increment the value by one. | ||
| 38114 | RET NZ | Return if any key has been pressed. | ||
| 38115 | DJNZ Debounce_Loop | Decrease the timeout counter by one and loop back to Debounce_Loop until the timeout counter is zero. | ||
| 38117 | RET | Return. | ||
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