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Routines |
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Used by the routine at check_user_input.
The whole keyboard is in use, a pair of half-rows to each action. The bottom row alternates: Z, C, B and M turn left, X, V, N and Symbol Shift turn right. A to G and H to Enter walk forward, Q to T and Y to P jump, and the number keys pick up and drop. Caps Shift and Space are left alone -- they are the pause keys (handle_pause).
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| keyboard | D0C8 | LD A,$FE | half-row Caps..V; Z to bit 0, X to bit 1, C to bit 2, V to bit 3 | |
| D0CA | CALL read_port | |||
| D0CD | RRCA | |||
| D0CE | LD C,A | Z and X | ||
| D0CF | AND $03 | |||
| D0D1 | SRL C | fold C onto Z and V onto X | ||
| D0D3 | SRL C | |||
| D0D5 | OR C | |||
| D0D6 | AND $03 | |||
| D0D8 | LD C,A | C = left and right so far; half-row B..Space | ||
| D0D9 | LD A,$7F | |||
| D0DB | CALL read_port | |||
| D0DE | BIT 1,A | Symbol Shift: right | ||
| D0E0 | JR Z,keyboard_m | |||
| D0E2 | SET 1,C | |||
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