Add extended keyboard handling description
tomaz opened this issue · comments
As matt mentioned, the Next matrix is actually 8x7 and normally the hardware is translating keys from those extra two columns into key combinations in the 8x5 subset so that normal spectrum key scanning continues to work. So EDIT is translated to CAPS+1, for example. You can turn that translation off however (nextreg 0x68 bit 4). The state of the extra keys can always be read via nextreg 0xb0 and 0xb1 https://gitlab.com/SpectrumNext/ZX_Spectrum_Next_FPGA/-/blob/master/cores/zxnext/nextreg.txt#L841
(note: as this will result in keyboard using multiple pages, "intentionally empty page" should be inserted before so that chapter starts on left side)