Z80asm is an assembler for Z80 assembly.
If no input files are specified, stdin is used. If no output file is
specified, "a.bin" is used. If "-" is specified as output file, stdout is
used. This makes it possible to use the assembler in a pipeline.
When multiple input files are specified, the assembler first uses all files
which were specified with -i or --input, in the order given. After that, all
files which were specified as non-option arguments are assembled, also in the
Show summary of options and exit.
Display version information and exit.
Be verbose. Specify multiple times to be more verbose. Messages are sent to
Write a list file. No filename or '-' means stderr.
Write a label file. No filename or '-' means stderr.
prefix all labels with this prefix.
Specify an input file (-i may be omitted). '-' means stdin.
Specify the output file. '-' or completely omitting the option means stdout.
Add a directory to the include path. The order in which the directories are
tried is from back to front: the last directory specified has the highest
priority. "/usr/share/z80asm" is always in the include path (with lowest
priority), you don't have to specify it.
Produce output even in case of errors. Normally the output, list and label
files are removed when assembly is unsuccesful.
All mnemonics and registers are case insensitive. All other text (in
particular, labels and macros) are not.
Undocumented opcodes are as much as possible supported:
sll and sli are equal and can both be used.
ixh, ixl, iyh and iyl can be used.
Assembler directives are:
Include a binary file into the resulting assembled file. This can be used to
include text files, or images, sound files, etc. The filename is searched for
in the current directory, and then in the include path, just like for include.
Also like for include, the quotes can be any character (but must match) and
no substitution is performed (so ~ is not your home directory).
defb or db arg, arg, arg, ...
defm or dm "String", 'String'
Define message. Each character in the string is stored as one byte. Backslash
escapes are allowed, as in characters in expressions. Unlike the argument for
include, the quotes must really be quotes (but they can be single or double
quotes. The closing quote must match the opening quote.)
defb/db and defm/dm are really aliases; either can take both
quoted strings and numbers:
defb "This text should be in a buffer\r\n", 0
defs or ds count [, value]
Define space. count bytes are reserved. Each of them is initialised to the
specified value, or 0 if no value is specified.
defw or dw arg, arg, arg, ...
Define words. Each argument is stored as two bytes, the low order byte first.
End assembly of this source file. Any remaining lines are copied into the list
file (if present), but not assembled.
label: equ expression
Define label to have value expression.
code block 1
code block 2
code block 3
code block n
Conditionally assemble code. If expression is not 0, all odd code blocks are
assembled, if expression is 0, all even blocks are assembled. Usually only
one or two code blocks are present.
Include file into the source. The quotes around the file for include are
mandatory, but you can choose the quotes yourself. eg, you may use % or even
a letter as a quote. The filename does not undergo any expansion, so \, ~,
$, etc are passed as written (which means ~ will not be your home directory.)
The filename is used as specified, and then prefixed with each directory in the include path, until it can be opened.
label: macro arg1, arg2, ...
Define a macro. The macro can be used where an opcode is expected. The code
block is then substituted, with the given values for the arguments. This is
a textual substitution, so the following example is valid:
This will generate a label with a constructed name (it's not a very useful
example, but it shows the possiblities).
Set the "program counter" to address. This does not add any bytes to the
resulting binary, it only determines how the rest of the code is interpreted
(in particular, the value of labels and
Seek to position offset in the output file. This can be used for overwiting
previously assembled code, for example for patching a binary which was included
All expressions can use the following operators, in order of precedence:
(a, b and c denote subexpressions)
a ? b : c
If a is not zero, return b, otherwise c
a | b
a ^ b
a & b
a == b, a = b, a != b
a <= b, a >= b, a < b, a > b
a << b, a >> b
a + b, a - b
addition and subtraction
a * b, a / b, a % b
multiplication, division and modulo
~a, +a, -a
bitwise not, no effect and negation
1 if label exists, 0 if it does not. This does not generate an error if label
does not exist. Note that this is usually evaluated immediately (if the rest
of the expression permits), and it does not check if the label is defined
later. This means it can be used as the argument of
, to get the functionality of #ifdef in C.
Literals in expressions may be written as: (case does not matter)
arbitrary base number (specified by 'c' so c+1 == 10: here base is 13)
14, 14d, @914
016, 16o, 16q, &o16, @716
0Eh, 0xE, &hE, $E, @FE
hexadecimal number (for the first notations, the first character must be 0-9)
%1110, 1110b, &b1110, @11110
ASCII code of 's'
'\\n', '\\r', '\\a', '\\t'
Newline, carriage return, alert, tab
Octal ASCII code
address of first byte of current command
In all expressions, labels may be used. However, there are some expressions
where the value must be computable at once, and therefore only previously
defined labels may be used. This is the case for:
- The argument of org
- The argument of seek
- The argument of equ (eg, a label definition)
- The first argument of ds
- The argument of if
In all other expressions, labels which are defined later may be used.
Labels must consist of letters, digits, underscores and periods, and must not
start with a digit. Labels are case sensitive.
Labels starting with a period (.) are
, which means their scope is only the current include file or macro definition
(and files included/macros called from it). This is particularly useful for
macros, to prevent duplicate definitions when using a macro more than once.
If assembly was successful, no output is produced (except the result, and
messages triggered by --verbose) and 0 is returned. At any error, there is
output on the standard error and 1 is returned.
Parts that are not assembled because of an if statement and macros which are
defined but never used are only checked to have a correct command. The
argument is not parsed. This means that if the file passes through the
assembler with no warnings or errors, it may still not assemble correctly in
a different setting (where the if's give different results).