KISS-TNC2

I really would like to have a simple re-implementation of ye olde TNC-2s that had a small eprom and a kiss mode TNC with a fricking BBS on ax-25 that worked like a charm. They existed I believe around 1988-1990ish. I mean, yes, this cable works with direwolf, but then I need to have a full linux system running, which I could do without for the purpose of an emergency comms system. I just found https://github.com/cheponis/KISS-TNC2, but I think this is just the KISS mode, not the AX25 stuff. I found https://www.ir3ip.net/iw3fqg/doc/wa8ded.htm which I think describes the TNC2S software I was running many years ago. Any other pointers would be great.

Congrats on taking this concept far beyond 'proof of concept'; well done. Done many years ago now, there is a preemptive multitasking OS for the Z80 for the "kiss TNC" used in ham radio: https://github.com/cheponis/KISS-TNC2/blob/master/KISS-TNC.a... This only used the interrupts to permit the modem (receive) side to generate interrupts, but the concepts are the same as if the interrupt would have come from a timer source. Yes, it uses the EXX and EX AF,AF' instructions. The best Z80 book, which describes the little-known W and Z registers is http://www.z80.info/zip/zaks_book.pdf start on page 86 for their description.