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<title>Using as: H8/300 Opcodes</title>
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Previous: <a href="H8_002f300-Directives.html#H8_002f300-Directives" accesskey="p" rel="prev">H8/300 Directives</a>, Up: <a href="H8_002f300_002dDependent.html#H8_002f300_002dDependent" accesskey="u" rel="up">H8/300-Dependent</a> &nbsp; [<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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<a name="Opcodes-7"></a>
<h4 class="subsection">9.12.5 Opcodes</h4>
<a name="index-H8_002f300-opcode-summary"></a>
<a name="index-opcode-summary_002c-H8_002f300"></a>
<a name="index-mnemonics_002c-H8_002f300"></a>
<a name="index-instruction-summary_002c-H8_002f300"></a>
<p>For detailed information on the H8/300 machine instruction set, see
<cite>H8/300 Series Programming Manual</cite>. For information specific to
the H8/300H, see <cite>H8/300H Series Programming Manual</cite> (Renesas).
</p>
<p><code>as</code> implements all the standard H8/300 opcodes. No additional
pseudo-instructions are needed on this family.
</p>
<a name="index-size-suffixes_002c-H8_002f300"></a>
<a name="index-H8_002f300-size-suffixes"></a>
<p>Four H8/300 instructions (<code>add</code>, <code>cmp</code>, <code>mov</code>,
<code>sub</code>) are defined with variants using the suffixes &lsquo;<samp>.b</samp>&rsquo;,
&lsquo;<samp>.w</samp>&rsquo;, and &lsquo;<samp>.l</samp>&rsquo; to specify the size of a memory operand.
<code>as</code> supports these suffixes, but does not require them;
since one of the operands is always a register, <code>as</code> can
deduce the correct size.
</p>
<p>For example, since <code>r0</code> refers to a 16-bit register,
</p><div class="example">
<pre class="example">mov r0,@foo
</pre><pre class="example">is equivalent to
</pre><pre class="example">mov.w r0,@foo
</pre></div>
<p>If you use the size suffixes, <code>as</code> issues a warning when
the suffix and the register size do not match.
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