Hello all

I have tried the suggestions, with success.
The timeline is as follows:
- my code completely still, but with bypass caps: no change
- without interrupts, just main doing the outputting: there it is.
- with the defensive programming as demonstrated by BigDumbDinosaur: it works, interrupts ...

Thank you for all the replies.

The construction is all wire wrapped (with no bypass caps), so spurious signals isn't out of the question.
All suggestions are appreciated and will be tried, starting with those darned bypass caps.

I will let you know the results thusly

Much thanks,
FFF

Hello everyone

I've built a simple SBC with a 65C02, 65C22, SST39SF020 for ROM, AS6C22256, and some NAND gates for address decoding.
I've been trying to output a sine lookup table on port A of the 65C22.
The weirdest thing is that when I reset the computer, some stuff happens on port A, but then at ...