cardiograph-computer/notes/todo.md

To do

Research

• Learn how the C64's PC gets initialized (what is the initial value? how is it set?)
• Review CHIP-8
  • read about the spec / ISA
  • read these, and add them to the bibliography:
    • Steve Losh: https://stevelosh.com/blog/2016/12/chip8-input/
    • https://tonisagrista.com/blog/2021/chip8-spec/

Documentation

• Improve docs for flags register
• Play with JSDoc

Design

• Add a flag for bank-switching to the ~zero-page
• Move the initial IP value, to eliminate the gap between it and the keypad pointer
• Consider adding a VIP-style keypad-based machine code monitor

For consideration

• Subroutine stack
• Extended system (secret bonus operations)

Programming

• Write some more complex test programs
  • Display (hex) numbers
  • Greater than
  • Minimal LOGO-ish interpreter for turtle graphics

Run-scripts

• Replace with running ./cpu.js and ./assembler.js diretly

Simulator

Assembler

• Validate labels
• Return pure machine code when printing to stdout (and not in debug mode)

CPU

• Add a mode that prints the display as text, but still animates

• Make single-stepping work with simulated keypad

• Allow running pre-compiled machine code

  I'm thinking of an interface like this...

    $ ./cpu.js -mc code.bin  
    $ ./cpu.js code.asm
    $ ./cpu.js --debug code.asm
  

  Full list of flags I want:

    -d --debug
    -s --singlestep
    -p --prettydisplay
    -mc --machinecode
  

Possible under-the-hood improvements

• Do a proper binary version... (or lose the typed arrays?)
• Extract debugging to its own module
• DRY out addition and subtraction