atasm [options] filename
atasm assembles 6502 code to an Atari DOS executable, an Atari XFD disk image, or a raw binary file.
The syntax used is compatible with the Atari 8-bit assembler MAC/65, with a few extensions (notably 6502 illegal opcode support)
saves the object file to filename instead of sourcefile [.65o]
Defines symbol to value before assembly begins. This is equivalent to inserting a line like symbol=value before the first line of the source file.
specifies a search directory for .INCLUDE directives
prints assembly trace.
prints symbol table when assembly is completed.
enables undocumented opcodes. This is equivalent to using the .OPTILL in the source file. Notice that this command-line paramter is overriden by any directives in the source files.
defines the template emulator state file.
saves object file to .XFD image filename
saves object code as a raw binary image
set the raw binary fill byte to value
This man page is nowhere near complete. For full documentation, see /usr/share/doc/atasm/atasm.txt