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<html>
<head>
<title>A09</title>
</head>
<body>
<h1>A09 - 6800/6801/6809/68HC11/6301/6309 Assembler</h1>
<p align="right">Copyright (c) 1993,1994 L.C. Benschop<br>
Parts Copyright (c) 2001-2020 Hermann Seib</p>
<p>Based on Lennart Benschop's C core that can be found somewhere on the 'net
(last address known to me was
<a href="http://koti.mbnet.fi/~atjs/mc6809/Assembler/A09.c">
http://koti.mbnet.fi/~atjs/mc6809/Assembler/A09.c</a>),
I built a complete Macro Assembler that is functionally better than the
TSC Flex9 Assembler (no wonder, I got multimegabytes to play with, whereas this
excellent piece of software works within 50K or so!). It can deliver binary,
Intel Hex, Motorola S1, and Flex9 binary output files, plus Flex9
RELASMB-compatible relocatable object modules.</p>
<p>I taylored the original to my taste by working through the source code; since
A09 has reached a level of complexity that doesn't really lend itself to following the "Use
the Source, Luke!" principle if you just want to hack a little 6809 assembly
program, I've added this documentation. Have fun!</p>
<p align="right">Hermann Seib, 2020</p>
<h2>Syntax</h2>
<pre>a09 [-{b|r|s|x|f}[filename]]|[-c] [-l[filename]] [-ooption]* [-dsym=value]* sourcefile*</pre>
<h3>Command Line Parameters</h3>
<dl>
<dt><b>-c</b></dt>
<dd>suppresses code output (corresponds to ASMB's <b>B</b> command line option)</dd>
<dt><b>-u</b></dt>
<dd>shorthand notation for the <b>UEX</b> option (see below)</b></dd>
<dt><b>-b<i>filename</i></b> (default output mode)</dt>
<dd>create a binary output file<br>
if no file name is given, the extension <b>.bin</b> is used (<b>.b</b> on
Unix)</dd>
<dt><b>-r<i>filename</i></b></dt>
<dd>create a Flex9 RELASMB-compatible output file name<br>
if no file name is given, the extension <b>.rel</b> is used</dd>
<dd><b>Attention:</b> this file format is undocumented; my solution has been
derived from some bits of information gathered on the Flex User Group mailing
list and a bit of playing with the original. In my tests, the output was
identical to RELASMB's; nevertheless, A09 <i>might</i> create modules that are
incompatible with the original under circumstances that I don't know or
haven't tested.</dd>
<dt><b>-s<i>filename</i></b></dt>
<dd>create a Motorola S-record output file name<br>
if no file name is given, the extension <b>.s09</b> is used</dd>
<dt><b>-x<i>filename</i></b></dt>
<dd>create an Intel hex output file name<br>
if no file name is given, the extension <b>.hex</b> is used</dd>
<dt><b>-f<i>filename</i></b></dt>
<dd>create Flex9 ASMB-compatible output file<br>
if no file name is given, the extension <b>.bin</b> is used</dd>
<dt><b>-l<i>filename</i></b></dt>
<dd>create a list file (default no listing)<br>
if no file name is given, the extension <b>.lst</b> is used</dd>
<dt><b>-d<i>sym</i>[=<i>value</i>]</b></dt>
<dd>define a symbol (see <b>TEXT</b> directive below) <br>
(roughly corresponds to ASMB's command line parameters 1-3)</dd>
<dt><b>-o<i>opt</i></b></dt>
<dd>defines an option (see below)</dd>
<dt><b>sourcefile</b></dt>
<dd>the assembler source file(s) to be processed.<br>
At least one source file must be given; the first one also defines
the default output and listing file names.</dd>
</dl>
<h2>Options</h2>
<p>Over the years, A09 has learned quite a lot, and it can handle source files /
list files in various formats. To allow their selection, I have expanded the
scope of the <b>OPT</b> directive (see the FLEX9 Assembler Manual that can be
found in the Documentation section on <a href="http://www.flexusergroup.com">
www.flexusergroup.com</a> for details). Here's the list of additional options
available in A09 (* denotes the default value for a mutually exclusive set):</p>
<table border="0" cellspacing="1" width="100%" id="AutoNumber1">
<tr>
<td valign="top" width="10%"><b>SYM *</b></td>
<td>print a symbol table</td>
</tr>
<tr>
<td valign="top"><b>NOS</b></td>
<td>suppress symbol table printing (corresponds to ASMB's <b>S</b> command
line option)</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>MUL *</b></td>
<td>print multiple object code lines</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>NMU</b></td>
<td>suppress printing of multiple object code lines (corresponds to ASMB's
<b>G</b> command line option)</td>
</tr>
<tr>
<td height="8" colspan="2" valign="top"></td>
</tr>
<tr>
<td valign="top"><b>LP1</b></td>
<td>print a Pass 1 listing</td>
</tr>
<tr>
<td valign="top"><b>NO1 *</b></td>
<td>print Pass 2 listing only</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>DAT</b> *</td>
<td>print current date on formatted pages</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>NOD</b></td>
<td>do not print the current date (corresponds to ASMB's <b>D</b> command
line option)</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr>
<td valign="top"><b>NUM</b></td>
<td>print line numbers (corresponds to ASMB's <b>N</b> command line option)</td>
</tr>
<tr>
<td valign="top"><b>NON *</b></td>
<td>do not print line numbers</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>INV</b></td>
<td>print invisible lines</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>NOI *</b></td>
<td>do not print invisible lines</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr>
<td valign="top"><b>TSC</b></td>
<td>strict TSC Assembler compatibility</td>
</tr>
<tr>
<td valign="top"><b>NOT *</b></td>
<td>accept source code in a much more relaxed format</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>WAR *</b></td>
<td>print warnings</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>NOW</b></td>
<td>only print errors, suppress warnings (corresponds to ASMB's <b>W</b>
command line option)</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr>
<td valign="top"><b>CLL *</b></td>
<td>check line length (see the <b>SETLI</b> directive on that)</td>
</tr>
<tr>
<td valign="top"><b>NCL</b></td>
<td>do not check line length</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>LFN</b></td>
<td>print long file names; on Win32 systems, this causes the file names
displayed in warning and error messages to contain the full path name of the
corresponding source file.</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>NLF *</b></td>
<td>do not print long file names</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr>
<td valign="top"><b>LLL *</b></td>
<td>list library file lines</td>
</tr>
<tr>
<td valign="top"><b>NLL</b></td>
<td>suppress listing of library file lines</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>GAS</b></td>
<td>accept Gnu AS-compatible source code<br>
this isn't fully implemented yet. At the moment, the only significant
difference is that A09 accepts constants in the form <b>0xXXXX</b> (hex), <b>
0bXXXX</b> (binary), <b>0NNN</b> (octal) in addition to the "standard" <b>$</b>,<b>%</b>,
or <b>@</b> notation.</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>NOG *</b></td>
<td>don't accept Gnu AS-compatible source code</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr>
<td valign="top"><b>REL *</b></td>
<td>print the relocation table if in Relocating Assembler mode</td>
</tr>
<tr>
<td valign="top"><b>NOR</b></td>
<td>suppress printing of the relocation table</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>M68|M09 *</b></td>
<td>both forms accept Motorola 6809 mnemonics</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>H63|H09</b></td>
<td>accept Hitachi 6309 mnemonics (still slightly experimental)</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>M00|M02|M08</b></td>
<td>accept Motorola 6800 mnemonics</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>M01|M03</b></td>
<td>accept Motorola 6801 mnemonics</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>H01|H03</b></td>
<td>accept Hitachi 6301 mnemonics (slightly experimental)</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>H11</b></td>
<td>accept Motorola 68HC11 mnemonics (very experimental)</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr>
<td valign="top"><b>TXT</b></td>
<td>print the text table if text symbols are defined (see <b>TEXT</b> directive)</td>
</tr>
<tr>
<td valign="top"><b>NTX *</b></td>
<td>do not print the text table</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>LPA</b></td>
<td>print listing in f9dasm/dasmfw patch format<br>
This option makes it easier to create complex patches to be embedded in images processed by f9dasm and dasmfw.
The PEMT directive can be used to generate additional info file statements.</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>NLP *</b></td>
<td>don't print listing in f9dasm patch format</td>
</tr>
<tr>
<td colspan="2" height="8" valign="top"></td>
</tr>
<tr>
<td valign="top"><b>DLM</b></td>
<td>define label on macro expansion; see
<a href="https:/Arakula/A09/issues/1" target="_blank">https:/Arakula/A09/issues/1</a>
for details.
</td>
</tr>
<tr>
<td valign="top"><b>NDL *</b></td>
<td>do not define labels on macro expansion</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>RED</b></td>
<td>allow redefinition of EQU statements to code/data labels <i>if</i> the value stays the same</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>NRD *</b></td>
<td>do not allow redefinition of EQU statements to code/data labels</td>
</tr>
<tr>
<td valign="top"><b>FBG *</b></td>
<td>fill gaps with the defined fill character in binary files</td>
</tr>
<tr>
<td valign="top"><b>NFB</b></td>
<td>do not fill gaps with the defined fill character in binary files<br />
<b>Note:</b> when used, A09 does not go back in the output file any more, so constructions like <br />
ORG $0100 (some code) ORG $0300 (some code) <b>ORG $0200</b> (some code)<br />
result in the code at $0200 to be <i>at the end</i> of the binary file.</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>UEX</b></td>
<td>automatically convert all undefined labels to external references if Flex9 RELASMB output is generated.<br />
This roughly corresponds to Flex9 RELASMB's U option. Setting this option is silently ignored in any other output mode.</td>
</tr>
<tr bgcolor="#f0f0f0">
<td valign="top"><b>NUE *</b></td>
<td>undefined labels are undefined labels and thus produce errors</td>
</tr>
</table>
<p>Each of the above options has a corresponding text symbol that is set to <b>0</b>
or <b>1</b>, corresponding to the state of the option. This allows for conditional
assembly, for example:</p>
<pre> IF &H63
LDW Data
SUBW #12
STW Data
ELSE
PSHS D
LDD Data
SUBD #12
STD Data
PULS D
ENDIF</pre>
<h2>Directives</h2>
<p>A09 handles the full set of directives available in the FLEX9 ASMB and
RELASMB programs (see the excellent Documentation section on
<a href="http://www.flexusergroup.com">www.flexusergroup.com</a> for the manuals
of these programs). Apart from these, it knows the following directives:</p>
<table border="0" cellspacing="1" id="AutoNumber1">
<tr>
<td valign="top" width="25%"><b><i>[label]</i> BIN <i>filename</i></b> or<br><b><i>[label]</i> BINARY <i>filename</i></b></td>
<td valign="top">loads the binary contents of the file given in <i>filename</i>
at the current position</td>
</tr>
<tr>
<td valign="top"><b>EXTERN <i>label</i></b></td>
<td valign="top">is implemented as an alias to the <b>EXT</b> directive (see
RELASMB documentation)</td>
</tr>
<tr>
<td valign="top"><b>FILL <i>value</i>,<i>bytecount</i></b></td>
<td valign="top">writes the 8-bit value <b><i>value</i></b> into <b><i>bytecount</i></b> consecutive memory locations<br />
<b>Note:</b> if <b><i>bytecount</i></b> exceeds 255 and <b>OPT MUL</b> (see above) is set, only the first 255 bytes are shown
in the listing.</td>
</tr>
<tr>
<td valign="top"><b>IFD, IFND <i>symbol</i>[,<i>skipcount</i>]</b></td>
<td valign="top">assembles the block up to the next <b>ELSE</b> or <b>ENDIF</b>
directive if the symbol is (not) defined.<br />
<b>Attention:</b> this directive is a little bit dangerous - if the symbol is defined
<i>after</i> the <b>IF(N)D</b> directive, phasing errors can occur!</td>
</tr>
<tr>
<td valign="top"><b>PEMT <i>text</i></td>
<td valign="top">if the LPA option is used, PEMT outputs additional info file statements.
<i>text</i> is inserted verbatim in the listing; there are some expansion capabilities,
however:
<ul>
<li><b>*</b> (an asterisk) is expanded to the current address in hex format.</li>
<li><b>@(...)</b> can be used to evaluate arbitrarily complex A09 expressions.<br />
Inside @(), an asterisk is expanded to the current address in hex format, too,
but with a leading $, as the expression is then evaluated by A09.<br />
The output of the expression is evaluated to a hexadecimal value, unless the
expression is formatted as @(...)<b>,d</b>, in which case the output is decimal.</li>
</ul>
</td>
</tr>
<tr>
<td valign="top"><b>PHASE <i>addr</i><br>DEPHASE</b></td>
<td valign="top">tells the assembler that the following code shall be executed at
the specified address. This "shifting" is switched off by the instruction
<b>DEPHASE</b>.<br>
This can be useful for generation of EPROM contents which contain overlayed code banks
where code has to be stored at an address in the EPROM (governed by <b>ORG</b>), but is
<i>executed</i> at a different address (governed by <b>PHASE</b>).</td>
</tr>
<tr>
<td valign="top"><b>REP</b>, <b>REPEAT<i> count</i></b></td>
<td valign="top">are implemented as aliases to the <b>RPT directive</b> (see ASMB
documentation)</td>
</tr>
<tr>
<td valign="top"><b>RZB</b>, <b>BSZ</b>, <b>ZMB <i>nnn</i></b></td>
<td valign="top">works like the <b>RMB</b> directive (see ASMB documentation), but
it doesn't only reserve memory, but also zeroes the reserved bytes<br />
<b>Note:</b> if <b><i>nnn</i></b> exceeds 255 and <b>OPT MUL</b> (see above) is set, only the first 255 bytes are shown
in the listing.</td>
</tr>
<tr>
<td valign="top"><b>SETLI <i>nnn</i></b></td>
<td valign="top">sets the line length for listings (see the <b>CLL</b> option above); <b>
<i>nnn</i></b> is the number of columns that can be printed in a line
(40-2000). If the <b>NCL</b> option is selected, A09 ignores the line width (default
is 80).</td>
</tr>
<tr>
<td valign="top"><b>SETPG <i>nnn</i></b></td>
<td valign="top">sets the page length for paginated listings (see the <b>PAG</b> option
in the ASMB documentation); <b><i>nnn</i></b> is the number of lines that
fit on a page (10-1000, default is 66).</td>
</tr>
<tr>
<td valign="top"><b>SYMLEN <i>nnn</i></b></td>
<td valign="top">sets the maximum number of significant symbol characters;
<b><i>nnn</i></b> is the number (6-32). For implications, see <b>Symbols</b> below.</td>
</tr>
<tr>
<td valign="top"><b><i>label</i> TEXT <i>text</i></b></td>
<td valign="top">this corresponds to the <b>-d<i>sym</i>[=<i>value</i>]</b> command line
option (see above).<p>The FLEX9 ASMB and RELASMB programs can accept up to 3
replacement strings from the command line; these can be used in the source
file as "dummy parameters" &A, &B, and &C (see section "COMMAND LINE
PARAMETERS" in the ASMB manual on page 50).</p>
<p>A09 can do more than that. The <b>-d</b> command line option and the <b>
TEXT</b> directive (which can, for example be given in a library file) allow
the definition of any number of text replacements (well... not really "any",
but 4000 should be no problem :-) which can then be used in the assembler
source as <b>&<i>label</i></b>.</p>
<p>In addition to all options (see above), the following constants are predefined:</p>
<table border="0" cellspacing="1" width="100%" id="AutoNumber2">
<tr>
<td valign="top"><b>&ASM</b></td>
<td>Name of the Assembler; contains <b>A09</b></td>
</tr>
<tr>
<td valign="top"><b>&VERSION</b></td>
<td>contains the A09 version number as a hex constant ($<i>vvss</i>,
vv being the main version and ss being the subversion; at the time of writing,
the version is <b>$012D</b>).</td>
</tr>
<tr>
<td valign="top"><b>&PASS</b></td>
<td>current pass; contains <b>1</b> or <b>2</b></td>
</tr>
<tr>
<td valign="top"><b>&FILCHR</b></td>
<td>filler character used for RMB areas in binary output files; defaults to <b>$00</b></td>
</tr>
</table>
<p>Please note that TEXT labels are internally stored with a preceding '&' to keep them separate
from normal labels, so the maximum length of a TEXT label is 31.</p>
</td>
</tr>
<tr>
<td valign="top"><b>TITLE <i>text</i></b></td>
<td valign="top">is implemented as an alias to the <b>NAM</b>, <b>TTL</b> directive (see
ASMB documentation)</td>
</tr>
</table>
<h2>Symbol Table Contents</h2>
<p>The symbol table produced by A09 is a bit more verbose than the original. For
each symbol, it lists the symbol<i> name</i>,<i> type</i>, and <i>value</i>. The
following symbol types can occur:</p>
<table border="0" cellspacing="1" width="100%" id="AutoNumber3">
<tr>
<td><b>00</b></td>
<td>constant value (from EQU)</td>
</tr>
<tr>
<td><b>01</b></td>
<td>variable value (from SET)</td>
</tr>
<tr>
<td><b>02</b></td>
<td>address within module (LABEL)</td>
</tr>
<tr>
<td><b>03</b></td>
<td>variable containing address</td>
</tr>
<tr>
<td><b>04</b></td>
<td>external label</td>
</tr>
<tr>
<td><b>05</b></td>
<td>variable containing external address</td>
</tr>
<tr>
<td><b>06</b></td>
<td>unresolved address</td>
</tr>
<tr>
<td><b>07</b></td>
<td>variable containing unresolved address</td>
</tr>
<tr>
<td><b>08</b></td>
<td>public label</td>
</tr>
<tr>
<td><b>09</b></td>
<td>macro definition</td>
</tr>
<tr>
<td><b>10</b></td>
<td>unresolved public label</td>
</tr>
<tr>
<td><b>11</b></td>
<td>parameter name</td>
</tr>
<tr>
<td><b>13</b></td>
<td>empty; should never occur</td>
</tr>
<tr>
<td><b>14</b></td>
<td>REG directive</td>
</tr>
<tr>
<td><b>15</b></td>
<td>TEXT directive (value is the index into the text table; if you want to
see the last used replacement text for this label, set the <b>TXT</b> option)
</td>
</tr>
<tr>
<td><b>18</b></td>
<td>Common data block name (value is the length of the common data block in
this case)</td>
</tr>
<tr>
<td><b>20</b></td>
<td>Common data RMB label (value is the offset in the common data block)</td>
</tr>
<tr>
<td><b>34</b></td>
<td>local label (multiple definitions are sorted based on their address)</td>
</tr>
<tr>
<td><b>38</b></td>
<td>unresolved local label</td>
</tr>
</table>
<h2>Relocation Table Contents</h2>
<p>The Relocation Table is something which doesn't exist in the original. When
in Relocating mode, A09 creates this table to show where a relocation is to be
applied. For each entry, A09 lists the <i>symbol name</i>, <i>type</i>, and the
<i>relocation address</i>. There can be a '-' prepended to the symbol name to
indicate that the symbol is to be <i>subtracted</i> from the value at the
relocation address (normally, the symbol is added). The relocation table uses
the same set of types as the symbol table.</p>
<h2>Things that are.. and things that aren't</h2>
<p>My version of A09 aims to reproduce the behaviour of the Flex9
ASMB and RELASMB products. As of now, it reproduces about 99% of the originals'
functionality, and surpasses them in some areas.
Some things still work slightly different or aren't implemented, however.</p>
<h4>Expression Operators</h4>
<p>In ASMB and RELASMB, ! denotes a "logical NOT operator"; "logical" in this
context means that each bit is inverted.<br />
A09's original core came with a slightly different syntax for that, which
obviously has its roots in the "C" language the assembler is written in;
there, ! denotes a logical NOT (meaning that everything that's not 0
results in 0, and zero results in 1) and ~ denotes a binary inversion, which
corresponds to the ! in TSC's assemblers.
<br />I decided to keep A09's syntax, as it is more versatile -
so ! has a slightly different meaning in A09 than in ASMB/RELASMB.</p>
<h4>Symbols</h4>
<p>A09 normally handles symbols with up to 32 significant characters.
This is far more than the 6 (ASMB) or 8 (RELASMB) places in the predecessors
and normally quite convenient, but it can cause problems when
<ul>
<li>dealing with old sources that rely on the old maximum to work</li>
<li>creating RELASMB-compatible relocatable modules</li>
</ul>
When creating RELASMB-compatible relocatable modules, the number of significant places
is automatically reduced to 8. To resolve issues with old sources, the <b>SYMLEN</b> directive
has been added in V1.10 (see above). The symbol table always shows the symbols reduced to the
number of significant places, since that's how they are treated internally.
</p>
<h4>Local Labels</h4>
<p>This nice feature of RELASMB has been added to A09, too.
Due to the completely different implementation, and since A09 doesn't have to
work in the extremely limited address space available to a 6809,
A09 isn't restricted to 100 local labels; you can define as many local labels as you want to.
The only restriction is that the length of the all-numeric symbol must be less than the number
of significant symbol characters (see above) so that the <b>B</b> and <b>F</b> character can
be appended in references to the local label.</p>
<h4>External Expressions</h4>
<p>When in Relocating Assembler mode, you can define <i>external labels</i> (i.e.,
labels that refer to a location in another module, that are resolved by the
Linker/Loader at a later time). These labels can be used in expressions, but in
a more restricted way than in RELASMB, due to the way the parser works. If there
is a mixture of relocatable and external elements in the expression, the
relocatable elements have to be in pairs so that they effectively cancel each
other's effect, just like in the original - but, additionally, the external
label has to be either the last element in the expression or the paired
relocatable elements have to be parenthesized. As an example,
<pre>rel1-rel2+ext1-rel2+rel1</pre> would be flagged as an error while
<pre>rel1-rel2-rel2+rel1+ext1
(rel1-rel2)+ext1-(rel2-rel1)</pre> would work.<p>The command line switch
that instructs RELASMB to treat all undefined labels as external labels isn't
implemented.</p>
<h4>Fix Mode</h4>
<p>RELASMB's Fix Mode is not implemented. While that may be a nifty feature, it
can easily be replaced by a combination of <b>TEXT</b> and <b>IF</b> directives,
which offer a better control over what gets assembled and what doesn't.</p>
<h4>Macros</h4>
<p>In RELASMB, nested macro definitions are allowed; in A09, they are not.
Nested macro calls, however, are possible; A09 allows up to 31 levels of macro call nesting.</p>
<p>Like in RELASMB, macros can be used to redefine mnemonics, but with a little twist
that is either missing in the original or undocumented: if the need arises to use the
original mnemonic in certain places, it can be prefixed with a backslash (\);
in this case, A09 doesn't check for macros but uses the original mnemonic.<br />
Prefixing a macro name that doesn't overload a mnemonic with \ leads to an error.</p>
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