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<title>Using as: M68HC11-Syntax</title>
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<a name="M68HC11_002dSyntax"></a>
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<div class="header">
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<p>
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Next: <a href="M68HC11_002dModifiers.html#M68HC11_002dModifiers" accesskey="n" rel="next">M68HC11-Modifiers</a>, Previous: <a href="M68HC11_002dOpts.html#M68HC11_002dOpts" accesskey="p" rel="prev">M68HC11-Opts</a>, Up: <a href="M68HC11_002dDependent.html#M68HC11_002dDependent" accesskey="u" rel="up">M68HC11-Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Syntax-17"></a>
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<h4 class="subsection">9.24.2 Syntax</h4>
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<a name="index-M68HC11-syntax"></a>
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<a name="index-syntax_002c-M68HC11"></a>
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<p>In the M68HC11 syntax, the instruction name comes first and it may
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be followed by one or several operands (up to three). Operands are
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separated by comma (‘<samp>,</samp>’). In the normal mode,
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<code>as</code> will complain if too many operands are specified for
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a given instruction. In the MRI mode (turned on with ‘<samp>-M</samp>’ option),
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it will treat them as comments. Example:
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</p>
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<div class="smallexample">
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<pre class="smallexample">inx
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lda #23
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bset 2,x #4
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brclr *bot #8 foo
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</pre></div>
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<a name="index-line-comment-character_002c-M68HC11"></a>
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<a name="index-M68HC11-line-comment-character"></a>
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<p>The presence of a ‘<samp>;</samp>’ character or a ‘<samp>!</samp>’ character anywhere
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on a line indicates the start of a comment that extends to the end of
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that line.
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</p>
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<p>A ‘<samp>*</samp>’ or a ‘<samp>#</samp>’ character at the start of a line also
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introduces a line comment, but these characters do not work elsewhere
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on the line. If the first character of the line is a ‘<samp>#</samp>’ then as
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well as starting a comment, the line could also be logical line number
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directive (see <a href="Comments.html#Comments">Comments</a>) or a preprocessor control command
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(see <a href="Preprocessing.html#Preprocessing">Preprocessing</a>).
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</p>
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<a name="index-line-separator_002c-M68HC11"></a>
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<a name="index-statement-separator_002c-M68HC11"></a>
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<a name="index-M68HC11-line-separator"></a>
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<p>The M68HC11 assembler does not currently support a line separator
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character.
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</p>
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<a name="index-M68HC11-addressing-modes"></a>
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<a name="index-addressing-modes_002c-M68HC11"></a>
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<p>The following addressing modes are understood for 68HC11 and 68HC12:
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</p><dl compact="compact">
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<dt><em>Immediate</em></dt>
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<dd><p>‘<samp>#<var>number</var></samp>’
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</p>
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</dd>
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<dt><em>Address Register</em></dt>
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<dd><p>‘<samp><var>number</var>,X</samp>’, ‘<samp><var>number</var>,Y</samp>’
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</p>
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<p>The <var>number</var> may be omitted in which case 0 is assumed.
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</p>
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</dd>
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<dt><em>Direct Addressing mode</em></dt>
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<dd><p>‘<samp>*<var>symbol</var></samp>’, or ‘<samp>*<var>digits</var></samp>’
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</p>
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</dd>
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<dt><em>Absolute</em></dt>
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<dd><p>‘<samp><var>symbol</var></samp>’, or ‘<samp><var>digits</var></samp>’
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</p></dd>
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</dl>
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<p>The M68HC12 has other more complex addressing modes. All of them
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are supported and they are represented below:
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</p>
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<dl compact="compact">
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<dt><em>Constant Offset Indexed Addressing Mode</em></dt>
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<dd><p>‘<samp><var>number</var>,<var>reg</var></samp>’
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</p>
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<p>The <var>number</var> may be omitted in which case 0 is assumed.
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The register can be either ‘<samp>X</samp>’, ‘<samp>Y</samp>’, ‘<samp>SP</samp>’ or
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‘<samp>PC</samp>’. The assembler will use the smaller post-byte definition
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according to the constant value (5-bit constant offset, 9-bit constant
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offset or 16-bit constant offset). If the constant is not known by
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the assembler it will use the 16-bit constant offset post-byte and the value
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will be resolved at link time.
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</p>
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</dd>
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<dt><em>Offset Indexed Indirect</em></dt>
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<dd><p>‘<samp>[<var>number</var>,<var>reg</var>]</samp>’
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</p>
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<p>The register can be either ‘<samp>X</samp>’, ‘<samp>Y</samp>’, ‘<samp>SP</samp>’ or ‘<samp>PC</samp>’.
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</p>
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</dd>
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<dt><em>Auto Pre-Increment/Pre-Decrement/Post-Increment/Post-Decrement</em></dt>
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<dd><p>‘<samp><var>number</var>,-<var>reg</var></samp>’
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‘<samp><var>number</var>,+<var>reg</var></samp>’
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‘<samp><var>number</var>,<var>reg</var>-</samp>’
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‘<samp><var>number</var>,<var>reg</var>+</samp>’
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</p>
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<p>The number must be in the range ‘<samp>-8</samp>’..‘<samp>+8</samp>’ and must not be 0.
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The register can be either ‘<samp>X</samp>’, ‘<samp>Y</samp>’, ‘<samp>SP</samp>’ or ‘<samp>PC</samp>’.
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</p>
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</dd>
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<dt><em>Accumulator Offset</em></dt>
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<dd><p>‘<samp><var>acc</var>,<var>reg</var></samp>’
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</p>
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<p>The accumulator register can be either ‘<samp>A</samp>’, ‘<samp>B</samp>’ or ‘<samp>D</samp>’.
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The register can be either ‘<samp>X</samp>’, ‘<samp>Y</samp>’, ‘<samp>SP</samp>’ or ‘<samp>PC</samp>’.
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</p>
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</dd>
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<dt><em>Accumulator D offset indexed-indirect</em></dt>
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<dd><p>‘<samp>[D,<var>reg</var>]</samp>’
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</p>
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<p>The register can be either ‘<samp>X</samp>’, ‘<samp>Y</samp>’, ‘<samp>SP</samp>’ or ‘<samp>PC</samp>’.
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</p>
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</dd>
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</dl>
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<p>For example:
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</p>
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<div class="smallexample">
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<pre class="smallexample">ldab 1024,sp
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ldd [10,x]
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orab 3,+x
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stab -2,y-
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ldx a,pc
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sty [d,sp]
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</pre></div>
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<hr>
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<div class="header">
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<p>
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Next: <a href="M68HC11_002dModifiers.html#M68HC11_002dModifiers" accesskey="n" rel="next">M68HC11-Modifiers</a>, Previous: <a href="M68HC11_002dOpts.html#M68HC11_002dOpts" accesskey="p" rel="prev">M68HC11-Opts</a>, Up: <a href="M68HC11_002dDependent.html#M68HC11_002dDependent" accesskey="u" rel="up">M68HC11-Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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