Daryl, yours is a fantastic design. I have one I had been working on and solimmed it down when I saw yours was through express pcb. For mine, it runs a little simpler using a 6522 instead of being able to switch, I also use a diagnostic LED which will flash on completing self tests. Also, it uses straight eprom instead of the flashram. The memomry mapping I redid yours but used a straight 74ls04 instead of other gates on the 74ls00. This allows me a reset buffering and a driver for the diagnostic LED. (the trick here you may find useful, the diagnostic LED is connected to A7, and the program merely flips back and forth along a $7f-$80 boundary to turn it off and on. The edge is now a single row of .100 pins instead of a double header, plus I bring out the extra cb1/2 and ca1/2 and /irq lines. Its a 25 pin connector there.
To date, I have it sucessfully completing a rom checksum and ram test at this point with a sucessful flash after each test. I am working on the 6522 self testing routine.
It will be used for pinball and arcade design.
Your SBC is fantastic and a good learning tool, plus its a good price for the board manufacture. Keep it on up!
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