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Routines |
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This tests for any key press.
Used by the routine at escaped.
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| keyscan_all | A58C | LD BC,$FEFE | Set B to $FE (initial keyboard half-row selector) and C to $FE (keyboard port number) | |||||
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Start loop
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| keyscan_all_0 | A58F | IN A,(C) | Read the port | |||||
| A591 | CPL | Complement the value returned to change it from active-low | ||||||
| A592 | AND $1F | Discard any non-key flags | ||||||
| A594 | RET NZ | Return with Z clear if any key was pressed | ||||||
| A595 | RLC B | Rotate the half-row selector ($FE -> $FD -> $FB -> .. -> $7F) | ||||||
| A597 | JP C,keyscan_all_0 | ...loop until the zero bit shifts out (eight iterations) | ||||||
| A59A | XOR A | No keys were pressed - return with Z set | ||||||
| A59B | RET | |||||||
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