6502 VS py65

The Apple 1 ROM is quite a tight piece of coding. Just 256 bytes which implements basic console IO, and memory editing in hex. And still two bytes left over.

One version with lots of comments: https://github.com/jefftranter/6502/blob/master/asm/wozmon/w...

You can see a classic assembly language space optimizing trick at PRBYTE. It first prints the upper half of the byte in hex with call to the PRHEX procedure, then falls through to PRHEX again to print the second half. Two entry points to a common routine.

The First Book of KIM programs

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.

Jeff Tranter has a github with a ton of stuff 6502, including a mini assembler. Many others out there as well.

Here’s a working one already https://github.com/mnaberez/py65

I use the cc65 toolset to program my 65c02 projects and the py65 emulator to help debug them. I use a slightly modified version of da65, the cc65 disassembler, to create a complete listing of my code, something I find very useful for multi-file projects.

I've recommended py65, by Mike Naberezny, for 6502 development and have created several enhancements to it for my own builds (interrupt handling and debug window). Unfortunately, py65 doesn't support the 65C816. Luckily, it's open source and easy to modify, so I thought I'd try adding support for the 65C816.

I didn't understand Python enough at the time. I could probably figure it out now that I know more, but those commands aren't really useful to me for how I use the monitor. I added the continue command which does what I wanted. Interestingly, someone requested that a continue command be added to py65 back in 2019.

Py65, by Mike Naberezny, is a great simulator for the 6502. I recommend checking it out, especially as your 6502 build and code get more advanced. Py65 doesn't handle interrupts though, so if your build uses them, you either need to create a version of your code to simulate or modify py65 to handle your hardware binary. The former is the best option for most people, but the latter might be attractive to folks who don't want to deal with two versions of their code.

Thanks for all of the info. It looks very interesting. I'll have to resist getting sidetracked. Not easy to do. I'm currently on another sidetrack adding interrupt capability to the py65 simulator. Not really needed, but it means I don't need to maintain a separate code base for the simulator. It has the added benefit of letting me work with Python.

I recommend cc65 as well and might as well mention the py65 emulator. Both are great tools that have aided my development.

Luckily there is a nice 6502 emulator, py65, that makes development easier. Without that I don't think I would have every attempted this. Once I got it running on the emulator it was fairly straight forward getting it to run on the breadboard 6502. Working on the actual hardware did provide some unique challenges though.

Thanks. I've been using py65 for my development.

I'll probably be working to get a version of this running in my ANSIish Forth in py65, a simulation of the 6502 in python. Py65 runs fine with terminal escape codes running in a compatible terminal program. I've tried it with Conway's Game of Life which works similarly.