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Routines |
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Annotated by Stephen Jones; Spectrum Discovery Club.
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| Keyboard_Test | 40019 | LD C,A | Key to test in C. | |
| 40020 | AND 7 | Mask bits d0-d2 for row. | ||
| 40022 | INC A | In range 1-8. | ||
| 40023 | LD B,A | Place in B. | ||
| 40024 | SRL C | Divide C by 8 to find position within row. | ||
| 40026 | SRL C | |||
| 40028 | SRL C | |||
| 40030 | LD A,5 | Only 5 keys per row. | ||
| 40032 | SUB C | Subtract position. | ||
| 40033 | LD C,A | Put into C. | ||
| 40034 | LD A,254 | High byte of port to read. | ||
| Keyboard_Find_Row | 40036 | RRCA | Rotate into position. | |
| 40037 | DJNZ Keyboard_Find_Row | Repeat until we've found the relevant row. | ||
| 40039 | IN A,(254) | Read port (A=high, 254=low). | ||
| Keyboard_Rotate_Loop | 40041 | RRA | Rotate bit out of result. | |
| 40042 | DEC C | Loop counter. | ||
| 40043 | JR NZ,Keyboard_Rotate_Loop | Repeat until bit for position in carry flag. | ||
| 40045 | RET | Return. | ||
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