If I've got a PS/2 connect to my spectrum then certain keys or buttons - like the NMI button - are mapped to either F-keys or key combinations.
This isn't a complete list, but useful (to me).
| Function | Key |
|---|---|
| NMI | F9 |
| Edit | Shift + 1 |
| Caps lock | Shift + 2 |
| Backspace | Shift + 0 |
| Break | Space |
Keys that are required when in some other mode that I don't know the name for (i.e. running .uart):
| Function | Key |
|---|---|
| Quote " | Ctrl + p |
| Plus + | Ctrl + k |
| Comma , | Ctrl + n |
| Period . | Ctrl + m |
| Colon : | Ctrl + z |
There's also this document that shows PS2 mappings to the spectrum, useful when you're forced to use the "48K style keys".