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97 lines
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97 lines
4.1 KiB
HTML
15 years ago
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<title>M68HC11-Modifiers - Using as</title>
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="M68HC11_002dDependent.html#M68HC11_002dDependent" title="M68HC11-Dependent">
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<link rel="prev" href="M68HC11_002dSyntax.html#M68HC11_002dSyntax" title="M68HC11-Syntax">
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<link rel="next" href="M68HC11_002dDirectives.html#M68HC11_002dDirectives" title="M68HC11-Directives">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
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2006, 2007 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 1.1
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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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<div class="node">
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<p>
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<a name="M68HC11_002dModifiers"></a>Next: <a rel="next" accesskey="n" href="M68HC11_002dDirectives.html#M68HC11_002dDirectives">M68HC11-Directives</a>,
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Previous: <a rel="previous" accesskey="p" href="M68HC11_002dSyntax.html#M68HC11_002dSyntax">M68HC11-Syntax</a>,
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Up: <a rel="up" accesskey="u" href="M68HC11_002dDependent.html#M68HC11_002dDependent">M68HC11-Dependent</a>
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<hr><br>
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</div>
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<h4 class="subsection">9.21.3 Symbolic Operand Modifiers</h4>
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<p><a name="index-M68HC11-modifiers-1163"></a><a name="index-syntax_002c-M68HC11-1164"></a>
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The assembler supports several modifiers when using symbol addresses
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in 68HC11 and 68HC12 instruction operands. The general syntax is
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the following:
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<pre class="smallexample"> %modifier(symbol)
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</pre>
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<a name="index-symbol-modifiers-1165"></a>
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<dl><dt><code>%addr</code><dd>This modifier indicates to the assembler and linker to use
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the 16-bit physical address corresponding to the symbol. This is intended
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to be used on memory window systems to map a symbol in the memory bank window.
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If the symbol is in a memory expansion part, the physical address
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corresponds to the symbol address within the memory bank window.
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If the symbol is not in a memory expansion part, this is the symbol address
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(using or not using the %addr modifier has no effect in that case).
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<br><dt><code>%page</code><dd>This modifier indicates to use the memory page number corresponding
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to the symbol. If the symbol is in a memory expansion part, its page
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number is computed by the linker as a number used to map the page containing
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the symbol in the memory bank window. If the symbol is not in a memory
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expansion part, the page number is 0.
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<br><dt><code>%hi</code><dd>This modifier indicates to use the 8-bit high part of the physical
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address of the symbol.
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<br><dt><code>%lo</code><dd>This modifier indicates to use the 8-bit low part of the physical
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address of the symbol.
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</dl>
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<p>For example a 68HC12 call to a function <span class="samp">foo_example</span> stored in memory
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expansion part could be written as follows:
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<pre class="smallexample"> call %addr(foo_example),%page(foo_example)
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</pre>
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<p>and this is equivalent to
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<pre class="smallexample"> call foo_example
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</pre>
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<p>And for 68HC11 it could be written as follows:
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<pre class="smallexample"> ldab #%page(foo_example)
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stab _page_switch
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jsr %addr(foo_example)
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</pre>
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</body></html>
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