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172 lines
5.9 KiB
HTML
172 lines
5.9 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This file documents the GNU Assembler "as".
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Copyright (C) 1991-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled "GNU Free Documentation License".
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-->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>AVR-Modifiers (Using as)</title>
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<meta name="description" content="AVR-Modifiers (Using as)">
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<meta name="keywords" content="AVR-Modifiers (Using as)">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="AS-Index.html#AS-Index" rel="index" title="AS Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="AVR-Syntax.html#AVR-Syntax" rel="up" title="AVR Syntax">
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<link href="AVR-Opcodes.html#AVR-Opcodes" rel="next" title="AVR Opcodes">
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<link href="AVR_002dRegs.html#AVR_002dRegs" rel="prev" title="AVR-Regs">
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</style>
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</head>
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<body lang="en">
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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="prev">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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</div>
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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 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 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 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 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 8 bit relocatable expression.
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This modifier useful for addressing data or code from
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Flash/Program memory. The using of ‘<samp>pm_lo8</samp>’ similar
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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 8 bit relocatable expression.
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This modifier useful for addressing data or code from
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Flash/Program memory.
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</p>
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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 8 bit relocatable expression.
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This modifier useful for addressing data or code from
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Flash/Program memory.
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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="prev">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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</div>
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</body>
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</html>
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