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<title>Using as: AVR-Modifiers</title>
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<a name="AVR_002dModifiers"></a>
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<div class="header">
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<p>
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Previous: <a href="AVR_002dRegs.html#AVR_002dRegs" accesskey="p" rel="previous">AVR-Regs</a>, Up: <a href="AVR-Syntax.html#AVR-Syntax" accesskey="u" rel="up">AVR Syntax</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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<hr>
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<a name="Relocatable-Expression-Modifiers"></a>
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<h4 class="subsubsection">9.5.2.3 Relocatable Expression Modifiers</h4>
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<a name="index-AVR-modifiers"></a>
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<a name="index-syntax_002c-AVR"></a>
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<p>The assembler supports several modifiers when using relocatable addresses
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in AVR instruction operands. The general syntax is the following:
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</p>
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<div class="smallexample">
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<pre class="smallexample">modifier(relocatable-expression)
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</pre></div>
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<dl compact="compact">
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<dd><a name="index-symbol-modifiers"></a>
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</dd>
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<dt><code>lo8</code></dt>
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<dd>
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<p>This modifier allows you to use bits 0 through 7 of
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an address expression as an 8 bit relocatable expression.
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</p>
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</dd>
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<dt><code>hi8</code></dt>
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<dd>
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<p>This modifier allows you to use bits 7 through 15 of an address expression
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as an 8 bit relocatable expression. This is useful with, for example, the
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AVR ‘<samp>ldi</samp>’ instruction and ‘<samp>lo8</samp>’ modifier.
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</p>
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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">ldi r26, lo8(sym+10)
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ldi r27, hi8(sym+10)
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</pre></div>
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</dd>
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<dt><code>hh8</code></dt>
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<dd>
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<p>This modifier allows you to use bits 16 through 23 of
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an address expression as an 8 bit relocatable expression.
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Also, can be useful for loading 32 bit constants.
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</p>
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</dd>
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<dt><code>hlo8</code></dt>
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<dd>
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<p>Synonym of ‘<samp>hh8</samp>’.
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</p>
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</dd>
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<dt><code>hhi8</code></dt>
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<dd>
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<p>This modifier allows you to use bits 24 through 31 of
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an expression as an 8 bit expression. This is useful with, for example, the
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AVR ‘<samp>ldi</samp>’ instruction and ‘<samp>lo8</samp>’, ‘<samp>hi8</samp>’, ‘<samp>hlo8</samp>’,
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‘<samp>hhi8</samp>’, modifier.
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</p>
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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">ldi r26, lo8(285774925)
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ldi r27, hi8(285774925)
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ldi r28, hlo8(285774925)
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ldi r29, hhi8(285774925)
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; r29,r28,r27,r26 = 285774925
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</pre></div>
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</dd>
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<dt><code>pm_lo8</code></dt>
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<dd>
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<p>This modifier allows you to use bits 0 through 7 of
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an address expression as an 8 bit relocatable expression.
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This modifier is useful for addressing data or code from
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Flash/Program memory by two-byte words. The use of ‘<samp>pm_lo8</samp>’
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is similar to ‘<samp>lo8</samp>’.
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</p>
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</dd>
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<dt><code>pm_hi8</code></dt>
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<dd>
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<p>This modifier allows you to use bits 8 through 15 of
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an address expression as an 8 bit relocatable expression.
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This modifier is useful for addressing data or code from
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Flash/Program memory by two-byte words.
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</p>
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<p>For example, when setting the AVR ‘<samp>Z</samp>’ register with the ‘<samp>ldi</samp>’
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instruction for subsequent use by the ‘<samp>ijmp</samp>’ instruction:
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</p>
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<div class="smallexample">
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<pre class="smallexample">ldi r30, pm_lo8(sym)
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ldi r31, pm_hi8(sym)
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ijmp
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</pre></div>
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</dd>
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<dt><code>pm_hh8</code></dt>
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<dd>
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<p>This modifier allows you to use bits 15 through 23 of
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an address expression as an 8 bit relocatable expression.
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This modifier is useful for addressing data or code from
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Flash/Program memory by two-byte words.
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</p>
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</dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Previous: <a href="AVR_002dRegs.html#AVR_002dRegs" accesskey="p" rel="previous">AVR-Regs</a>, Up: <a href="AVR-Syntax.html#AVR-Syntax" accesskey="u" rel="up">AVR Syntax</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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