Close but no cigar
I’m using the original olduino board to exercise the cpu card so I can see what it reads and writes. I have a little routine loaded in the avr that resets the 1802, switches to load, puts 0x55 on the bus, and loops pressing ‘IN’. Before I fixed this last issue I was consistently reading FFs. Now I get a hodgepodge of values probably indicating that my writes to memory aren’t working so i’m reading back whatever was there before. Still, mustn’t grumble.
ok, ok, wait. I hadn’t clipped the trace from pin 9 of the 4093 to pin 5 of the 4013. I bet *that’s* it!