TaliForth2 VS of816

Note that I've coded the debug window to work with my hardware binary which supports interrupts. As such it's somewhat specialized to my build and likely wouldn't work with your build without modification. Let me know if you're interested and I could point out changes needed for you build. Alternatively, I could fork the py65 GitHub and prepare a working version with my build's binary. As an added benefit you could play with my Forth operating system (though if your main interest is that then I'd recommend some better tested versions for the 6502, like Tali Forth 2 for example).

For a command line program I started out with getting WOZMON working and then began adding more capabilities similar to the Apple II system of old. I got tired of adding one-off functionality and discovered Forth when looking at programming languages suited for systems with limited resources. Look into TaliForth2 to get up and running fast on your 6502. The full program requires 24k ROM but can be slimmed down to fit in 16k pretty easily. I was inspired so I wrote my own Forth 2012 Standard version over the summer.

Get Taliforth running on it

I got tired of creating one-off functionality so I'm now working with Forth which is kind of like an operating system/programming language combined. It's pretty easing to get a version of that running on your 6502. Tali Forth 2 by Scott Stevenson ports pretty easily and has an editor, assembler and disassembler.

I also found this Forth implementation that might work.

There are several Forth versions for the 65816 that I've found online. Some are specialized to specific hardware but can be modified. Michael Guidero's OF816 is designed to be easily ported to new systems. I got it running on my 65816 emulator without much problem. It handles banked memory and uses a good subset of 65816 features.

One issue I had when I was finishing up my emulator was finding substantial programs to test that weren't designed for a particular architecture. I'm focused mainly on text-based programs, so it might not be as interesting for your emulation, but OF816, by Michael Guidero, is a larger program designed to be easily ported to new 65816-based systems. Here's my fork of it for my py65816 emulator as another example of porting it to an emulator. If you don't want to bother creating your own port or creating a binary, here's one with I/O mapped to 7FC0 and 7FE0 respectively. Load it at $8000 and reset to start. It uses bank 0 and bank 1 so you need to have at least those modeled.