/cch/ - Casio Calculator Hacking

If you take a look in an emulator ROM (the ROM that comes with Casio official emulators), you may find weird error strings, including strings like "SD Card is protected", "invarid Error" (sic), …

Why are they there?

Actually, it's part of Casio's custom emulator keyboard system; basically, yes, it's a debug feature. If you take a look at address 9838H (data segment depends on model type) you will see these get written there whenever there is an error.