debian | ||
.gitignore | ||
Makefile | ||
README.md | ||
xasm.1.txt | ||
xasm.d | ||
xasm.properties | ||
xasm.spec |
xasm
xasm is a 6502 cross-assembler with original syntax extensions. By default it generates binaries for Atari 8-bit computers.
Syntax
6502 assembly language is full of LDA, STA, LDA, STA sequences. With xasm you can use MVA as a shortcut for an LDA/STA pair or even MWA for 16-bit transfers. You can avoid defining labels when you need short jumps, thanks to conditional skip and repeat pseudo-instructions. You can put two instructions that share their argument in one line. These are just some of the features that help you program in a more concise way. Let's look at typical 6502 code (which is also valid in xasm):
lda #<dest
sta ptr
lda #>dest
sta ptr+1
ldx #192
do_line
ldy #39
do_byte
lda pattern,y
sta (ptr),y
dey
bpl do_byte
lda #40
clc
adc ptr
sta ptr
bcc skip
inc ptr+1
skip
dex
bne do_line
Using xasm's features this code can be rewritten to:
mwa #dest ptr
ldx #192
do_line
ldy #39
mva:rpl pattern,y (ptr),y-
lda #40
add:sta ptr
scc:inc ptr+1
dex:bne do_line
xasm syntax is based on 1990's Quick Assembler.
Write accumulator shifts as in asl @
.
Whitespace is important: it is required before the instruction
and disallowed in the operands, because it separates a comment from the operand, e.g.
lda #0 this is a comment, no need for a semicolon
This may look weird at first, but it enables nice features such as instruction pairs and two-argument pseudo-instructions.
Usage
xasm is a command-line tool. Therefore you additionally need a programmer's text editor.
I use SciTE.
To install xasm syntax highlighting and single-keystroke compilation,
copy xasm.properties
to the SciTE directory.
For single source file programs, press Ctrl+F7 to compile. You can double-click error messages to go to the incorrect line. Press F5 to run the program in the emulator.
For larger projects, I use GNU Make. Press F7 to build (and possibly run)
a project as described in the Makefile
. You can find my Makefiles in
my repositories on GitHub.
Download
A release is coming soon. Meanwhile you can download Windows binaries from the old website.
Links
- Atari800 - portable emulator of Atari 8-bit computers
- Atari XL/XE Source Archive - source code of Atari demos, utilities and games
- cc65 - C cross-compiler targeting 6502-based systems
- MADS - another 6502/65816 cross-assembler, partially supporting xasm's syntax
- WUDSN IDE - Eclipse plugin, front-end to several 6502 cross-assemblers including xasm