git clone 'https://github.com/redline6561/cl-6502.git'
cl-6502 is a Common Lisp emulator, assembler and disassembler for the MOS 6502 processor. In case that sounds weird to you, the MOS 6502 is famous for its use in…
I gave a talk on cl-6502 called ‘On Programmer Archaeology’. You can watch it on Vimeo or grab the slides. A few notes on why I'm writing it are here and minor notes on the design are here.
Inspired by Luke Gorrie's call for Readable Programs, there is a readable PDF book of the source. You can also produce it from the git repo with:
cd repo/src && make book. You'll need make, pandoc, and some latex packages (texlive-luatex, texlive-xetex, and texlive-latex-extra on debian) installed to build it yourself.
You are strongly encouraged to use this library via Quicklisp. Simply start your lisp and run:
ANDso you likely don't want to
:useit in your own packages.
In particular, asm, disasm, execute, step-cpu, and reset are likely of interest.
(asm "brk")) to get a bytevector to execute.
(setf (get-range 0) *my-bytevector*).
(setf (6502:cpu-pc *cpu*) 0).
(run *cpu*)or manually step through it with
(step-cpu *cpu* (get-byte (cpu-pc *cpu*))).
(reset)the CPU as necessary and keep hacking! :)
There are sexp-based and string-based assemblers, both invoked via
asm. The string-based assembler expects statements to be separated by newlines. The sexp-based assembler expects each statement to be in its own list. Disassembling to both formats is supported via
disasm-to-list. Semicolons are treated as “comment to end-of-line” in the string assembler.
| Addressing Mode | SEXP-based format | String format | |-----------------|-------------------|----------------| | Implied | (:brk) | "brk" | | Immediate | (:lda :#$00) | "lda #$00" | | Accumulator | (:rol :a) | "rol a" | | Zero-page | (:lda :$03) | "lda $03" | | Zero-page, X | (:lda :$03.x) | "lda $03, x" | | Zero-page, Y | (:ldx :$03.y) | "ldx $03, y" | | Absolute | (:sbc :$0001) | "sbc $0001" | | Absolute, X | (:lda :$1234.x) | "lda $1234, x" | | Absolute, Y | (:lda :$1234.y) | "lda $1234, y" | | Indirect | (:jmp :@1234) | "jmp ($1234) | | Indirect, X | (:lda :@12.x) | "lda ($12), x" | | Indirect, Y | (:lda :@34.y) | "lda ($34), y" | | Relative | (:bne :&fd) | "bne &fd" |
local-projectssubdirectory of quicklisp.
To run the tests, after you've loaded cl-6502 just run
(asdf:oos 'asdf:test-op 'cl-6502). You may need to
(ql:quickload 'cl-6502-tests) to ensure that the fiveam dependency is satisfied first.
The code is under a BSD license except for docs/6502.txt and tests/6502_functional_test.a65 which are only present by ‘mere aggregation’ and not strictly part of my sources.