Project author here, I agree. This was a toy project that I allocated a fixed amount of time to, hence the cut corners. I'm working on another design that uses

Project author here, I agree. This was a toy project that I allocated a fixed amount of time to, hence the cut corners. I'm working on another design that uses programmable logic to handle multiple interrupt sources (yes, including an NMI button) and allow either ROM or RAM to be banked into address 0.