This is a routine which scans the keyboard directly. It is approximately 8% faster then the firmware routine and doesn't enable interrupts.
Input: A = layer (&40 - &49)
Output: A = hardware keyboard value
Destroyed: BC
Hardware scancode table
| Value: Layer |
&7F | &BF | &DF | &EF | &F7 | &FB | &FD | &FE |
| &40 | (ZB) | ENTER | F3 | F6 | F9 | CURDOWN | CURRIGHT | CURUP |
| &41 | F0 | F2 | F1 | F5 | F8 | F7 | COPY | CURLEFT |
| &42 | CONTROL | \ | SHIFT | F4 | ] | RETURN | [ | CLR |
| &43 | . | / | : | ; | P | @ | - | ^ |
| &44 | , | M | K | L | I | O | 9 | 0 |
| &45 | SPACE | N | J | H | Y | U | 7 | 8 |
| &46 | V | B | F | G | T | R | 5 | 6 |
| &47 | X | C | D | S | W | E | 3 | 4 |
| &48 | Z | CAPSLOCK | A | TAB | Q | ESC | 2 | 1 |
| &49 | DEL | - | - | - | - | - | - | - |
Scanning routine
ld a, layer ;use the value from the table above ld bc, &F6C0 out (c), c ld bc, &F40E out (c), c ld bc, &F792 out (c), c ld b, &F6 out (c), c ld b, &F4 in a, (c) ld bc, &F782 out (c), c ld bc, &F600 out (c), c ;now check for the value from the table ;e.g. with 'cp <value>' ;and a condition ;e.g. 'jp <condition>, xxxx' or 'call <condition>, xxxx'