xais Andre Fachat's open-source 6502 cross assembler. I, Cameron Kaiser (email@example.com), am the current maintainer, and bug reports and questions should now go to me.
xa is Copyright © 1989-2023, André Fachat,
Jolse Maginnis, David Weinehall and Cameron Kaiser. All rights reserved.
Additional contributors: Fabien Nuñez, Mikkel Holm Olsen,
Adam Sampson, Alessandro Gatti, Simon Rowe, Dan Horák, Frederic Cambus,
Sam Falvo, Stephen Kitt, Bas Wassink, Sergei Trofimovich, Tom Hargreaves.
xa is distributed under the
GNU Public License v2. The current maintainer is
For other Floodgap-maintained packages, see the Floodgap Software listing.
xais a high-speed, two-pass portable cross-assembler. It understands mnemonics and generates code for NMOS 6502s (such as 6502A, 6504, 6507, 6510, 7501, 8500, 8501, 8502 ...), CMOS 6502s (65C02 and Rockwell R65C02) and the 65816.
Key amongst its features:
o65relocatable objects with a full linker and relocation suite, as well as "bare" plain binary object files
xa's eventual companion disassembler is
dxa, a moderately hacked-up version of Marko Mäkelä's
d65disassembler. This is still alpha and is available as a separate distribution until it is stabilized enough to be part of the
xa2.3.x. Didn't you believe me?
2.4.0 is a significant update of the code base with many new features. However, because this is more than just a point release, there are potentially incompatibilities with edge cases in 2.3 and earlier versions, and features that were declared deprecated in 2.3 have been removed.
xa should compile out of the box on just about any Unix or
Unixy thing, and will probably compile on other systems that support ANSI
C as well. Please see the
README.1st file for more detailed
instructions. It is tested and validated on AIX (gcc),
Linux/ppc64le (gcc and clang), Mac OS X
(gcc on PowerPC, and clang
on Intel x86_64 and Apple silicon) and NetBSD/macppc and
-F) in plain text or HTML, along with
.listbytesto control how hex bytes get listed in the output.
-Ecommandline option to not stop after 20 errors, but show all of them.
-Xcompatibility set command line option to distinguish between MASM and CA65 compatibility options; also adds C option for
0to specify hex or octal. As a result,
-Mis now deprecated, and colons in comments may become the default in a future version.
:=" label definitions, and various pseudo-opcodes (
.proc (anonymous only),
-Uoption to allow all undefined labels in relocating mode; this allows exporting them to an
.o65file and link at a later time (or specify one at a time with
#errorallows preprocessor-level assertions.
.assertallows assembler-level assertions.
makein tests, incorporating a patch from Sergei Trofimovich.
-XXA23, which is obviously deprecated.
\(backslash), except if
/* */comments are no longer allowed, except if
XA_MINORpredefined macros, except if
doc/archive are now in
attic/, which is the repository for old unsupported components. It may be purged in a future version.
-Mis now deprecated (use
-XMASM), just in case you forgot.
printcbm(1)is now deprecated (use VICE
petcat, it does a lot more).
-x) finally removed. If you need this support, you must use 2.3.x.
manformat since 2.3.0. You can read them here, converted with
"I developed the first version of xa on my old Atari ST to build programms for my selfbuilt computer CS/A65. After my Atari broke I ported it to Linux (ported? It compiled right out of the box!) and when I had to develop a programm for a friend of mine, I compiled it on an Amiga without errors. Until the beginning of 1992 I made more improvements, until it came to version 2.0.7. Since then I only very occasionally worked on it, up to version 2.0.7d. When I decided to push my selfbuilt OS to a new level in 1996, I needed more important improvements, like o65 object format and a linker and all that."
xais now officially accompanied by
dxa, its companion disassembler.
dxais a rudely hacked version of Marko Mäkelä's
d65package, with some extra features and altered output to allow "perfect" disassembly (which is to say, you can take an arbitrary object, run it through
dxa, take what it spits out, run it back through
xa, and get the binary you started with). It also has features for intelligently labeling code and data sections and multiple output formats, and can understand undocumented and CMOS opcodes (65816 not yet).
dxa is new and not well tested, I have not included it
as part of the standard
xa distribution and it is offered here
separately. Please consider it to be alpha software only and expect bugs.
Refer to the readme for instructions on installation.
d65, is distributed under GPL v2.
There are also many fixes in this version, including properly getting the very
last byte for files that load all the way to $ffff and correctly
(IMNSHO) truncating files that load beyond (thanks Malte), fixes for bugs with
clang-built dxa generating incorrect code, fixes for an
issue with the C preprocessor, and more flexible BASIC header detection.
Note that clang-built dxa does behave differently than
gcc-built dxa and more research is needed (currently the
only guarantee is that both will generate an assembly file which will
assemble to identical binaries).
dxa is based on
manformat; here is the