cl-6502, or The 6502...IBM 704 edition ;)
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 and related ideas which is online here. The slides are available separately here. A few notes on why I'm writing it are here and minor notes on the design are here.
Install You are strongly encouraged to use this library via Quicklisp. Simply start your lisp and run:
- Check out the docs for the cl-6502 package or have a look on quickdocs.
- Play around at the REPL!
- Use it to create your own wacky code artifacts.
- There is also a lower-level 6502 package if you really want to get your hands dirty. NOTE: The 6502 package shadows
AND so you likely don't want to
:use it in your own packages.
In particular, asm, disasm, execute, 6502-step, and reset are likely of interest.
A simple example:
- Load cl-6502 and switch to the
- Write some 6502 code and run it through
) to get a bytevector to execute.
- Load it into memory and run it with
(execute *cpu* *my-bytevector*)
- Load it with
(setf (get-range 0) *my-bytevector*)
- Set the program counter to 0 with
(setf (6502:cpu-pc *cpu*) 0)
- Manually step through it with
(6502-step *cpu* (get-byte (6502:immediate *cpu*)))
the CPU as necessary and keep hacking! :)
Supported Assembler Syntax 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" |
- Using Quicklisp: For local development, git clone this repository into the
subdirectory 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
to ensure that the fiveam dependency is satisfied first.
The code is under a BSD license except for docs/6502.txt and tests/6502functionaltest.a65 which are only present by 'mere aggregation' and not strictly part of my sources.