CHIP-8 in Common Lisp: Debugging Infrastructure

Our CHIP-8 emulator in Common Lisp is coming along nicely. It can play games, and in the last post we added a disassembler so we can dump the code of ROMs.
In this post we’ll add some low-level debugging infrastructure so we can set breakpoints and step through code.
The full series of posts so far:
CHIP-8 in Common Lisp: The CPU CHIP-8 in Common Lisp: Graphics CHIP-8 in Common Lisp: Input CHIP-8 in Common Lisp: Sound CHIP-8 in Common Lisp: Disassembly CHIP-8 in Common Lisp: Debugging Infrastructure CHIP-8 in Common Lisp: Menus The full emulator source is on BitBucket and GitHub.