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<title>H8/300 Opcodes (Using as)</title>

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<a name="H8_002f300-Opcodes"></a>
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<hr>
<a name="Opcodes-8"></a>
<h4 class="subsection">9.14.5 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.
</p>


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