Earlier in the year I build a Rosco 68000 computer board, which re-ignited my interest in home computing from the days when home computers were quite simple. I also found a source for MC6859 DES encryption chips (which I remember reading about in the early 80's), and a plan started to form. I soon found the Grant Searle web pages and then the blog pages byJeff Tranter, and I was hooked.
A 6809 computer running Flex or similar was a realistic target, and relatively modern components mean this can fit on a single PCB. 74HC logic eliminates the need for lots of buffers, large memory chips are cheap and Compact Flash is a practical floppy drive replacement.
I'm sharing all of the files for this project as I go, as well as a commentary on my progress, so hopefully the process will be of interest to some people.
Hi Phil, I found some issues with your CF-card software also but it helped me to write a little OS for the 6809. It works, but isn't ready for publication yet. For others to take part of it I published it on github. Only one slice (of 1.3MB) is supported due to a shortage of memory. (The OS resides from $8000-$BFFF) I use a buffer of 4KB for the directory and this consumes a lot of memory. I would be happier with a complete FAT12 or FAT16 based software written in assembly-code. I can give you the working CF-card software part back, that is working and tested. I use my own monitor so the I/O calls looks different then yours. It is part of the OS I wrote. You can find it here: https://github.com/nbrok/DOS09/blob/main/cfcard.asm