<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
<html>
|
<!-- Copyright (C) 1988-2016 Free Software Foundation, Inc.
|
|
Permission is granted to copy, distribute and/or modify this document
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
any later version published by the Free Software Foundation; with the
|
Invariant Sections being "Funding Free Software", the Front-Cover
|
Texts being (a) (see below), and with the Back-Cover Texts being (b)
|
(see below). A copy of the license is included in the section entitled
|
"GNU Free Documentation License".
|
|
(a) The FSF's Front-Cover Text is:
|
|
A GNU Manual
|
|
(b) The FSF's Back-Cover Text is:
|
|
You have freedom to copy and modify this GNU Manual, like GNU
|
software. Copies published by the Free Software Foundation raise
|
funds for GNU development. -->
|
<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
|
<head>
|
<title>Using the GNU Compiler Collection (GCC): MeP Variable Attributes</title>
|
|
<meta name="description" content="Using the GNU Compiler Collection (GCC): MeP Variable Attributes">
|
<meta name="keywords" content="Using the GNU Compiler Collection (GCC): MeP Variable Attributes">
|
<meta name="resource-type" content="document">
|
<meta name="distribution" content="global">
|
<meta name="Generator" content="makeinfo">
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
<link href="index.html#Top" rel="start" title="Top">
|
<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
<link href="Variable-Attributes.html#Variable-Attributes" rel="up" title="Variable Attributes">
|
<link href="Microsoft-Windows-Variable-Attributes.html#Microsoft-Windows-Variable-Attributes" rel="next" title="Microsoft Windows Variable Attributes">
|
<link href="M32R_002fD-Variable-Attributes.html#M32R_002fD-Variable-Attributes" rel="prev" title="M32R/D Variable Attributes">
|
<style type="text/css">
|
<!--
|
a.summary-letter {text-decoration: none}
|
blockquote.smallquotation {font-size: smaller}
|
div.display {margin-left: 3.2em}
|
div.example {margin-left: 3.2em}
|
div.indentedblock {margin-left: 3.2em}
|
div.lisp {margin-left: 3.2em}
|
div.smalldisplay {margin-left: 3.2em}
|
div.smallexample {margin-left: 3.2em}
|
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
|
div.smalllisp {margin-left: 3.2em}
|
kbd {font-style:oblique}
|
pre.display {font-family: inherit}
|
pre.format {font-family: inherit}
|
pre.menu-comment {font-family: serif}
|
pre.menu-preformatted {font-family: serif}
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
pre.smallexample {font-size: smaller}
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
pre.smalllisp {font-size: smaller}
|
span.nocodebreak {white-space:nowrap}
|
span.nolinebreak {white-space:nowrap}
|
span.roman {font-family:serif; font-weight:normal}
|
span.sansserif {font-family:sans-serif; font-weight:normal}
|
ul.no-bullet {list-style: none}
|
-->
|
</style>
|
|
|
</head>
|
|
<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
|
<a name="MeP-Variable-Attributes"></a>
|
<div class="header">
|
<p>
|
Next: <a href="Microsoft-Windows-Variable-Attributes.html#Microsoft-Windows-Variable-Attributes" accesskey="n" rel="next">Microsoft Windows Variable Attributes</a>, Previous: <a href="M32R_002fD-Variable-Attributes.html#M32R_002fD-Variable-Attributes" accesskey="p" rel="prev">M32R/D Variable Attributes</a>, Up: <a href="Variable-Attributes.html#Variable-Attributes" accesskey="u" rel="up">Variable Attributes</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
</div>
|
<hr>
|
<a name="MeP-Variable-Attributes-1"></a>
|
<h4 class="subsection">6.32.7 MeP Variable Attributes</h4>
|
|
<p>The MeP target has a number of addressing modes and busses. The
|
<code>near</code> space spans the standard memory space’s first 16 megabytes
|
(24 bits). The <code>far</code> space spans the entire 32-bit memory space.
|
The <code>based</code> space is a 128-byte region in the memory space that
|
is addressed relative to the <code>$tp</code> register. The <code>tiny</code>
|
space is a 65536-byte region relative to the <code>$gp</code> register. In
|
addition to these memory regions, the MeP target has a separate 16-bit
|
control bus which is specified with <code>cb</code> attributes.
|
</p>
|
<dl compact="compact">
|
<dt><code>based</code></dt>
|
<dd><a name="index-based-variable-attribute_002c-MeP"></a>
|
<p>Any variable with the <code>based</code> attribute is assigned to the
|
<code>.based</code> section, and is accessed with relative to the
|
<code>$tp</code> register.
|
</p>
|
</dd>
|
<dt><code>tiny</code></dt>
|
<dd><a name="index-tiny-variable-attribute_002c-MeP"></a>
|
<p>Likewise, the <code>tiny</code> attribute assigned variables to the
|
<code>.tiny</code> section, relative to the <code>$gp</code> register.
|
</p>
|
</dd>
|
<dt><code>near</code></dt>
|
<dd><a name="index-near-variable-attribute_002c-MeP"></a>
|
<p>Variables with the <code>near</code> attribute are assumed to have addresses
|
that fit in a 24-bit addressing mode. This is the default for large
|
variables (<code>-mtiny=4</code> is the default) but this attribute can
|
override <code>-mtiny=</code> for small variables, or override <code>-ml</code>.
|
</p>
|
</dd>
|
<dt><code>far</code></dt>
|
<dd><a name="index-far-variable-attribute_002c-MeP"></a>
|
<p>Variables with the <code>far</code> attribute are addressed using a full
|
32-bit address. Since this covers the entire memory space, this
|
allows modules to make no assumptions about where variables might be
|
stored.
|
</p>
|
</dd>
|
<dt><code>io</code></dt>
|
<dd><a name="index-io-variable-attribute_002c-MeP"></a>
|
</dd>
|
<dt><code>io (<var>addr</var>)</code></dt>
|
<dd><p>Variables with the <code>io</code> attribute are used to address
|
memory-mapped peripherals. If an address is specified, the variable
|
is assigned that address, else it is not assigned an address (it is
|
assumed some other module assigns an address). Example:
|
</p>
|
<div class="smallexample">
|
<pre class="smallexample">int timer_count __attribute__((io(0x123)));
|
</pre></div>
|
|
</dd>
|
<dt><code>cb</code></dt>
|
<dt><code>cb (<var>addr</var>)</code></dt>
|
<dd><a name="index-cb-variable-attribute_002c-MeP"></a>
|
<p>Variables with the <code>cb</code> attribute are used to access the control
|
bus, using special instructions. <code>addr</code> indicates the control bus
|
address. Example:
|
</p>
|
<div class="smallexample">
|
<pre class="smallexample">int cpu_clock __attribute__((cb(0x123)));
|
</pre></div>
|
|
</dd>
|
</dl>
|
|
<hr>
|
<div class="header">
|
<p>
|
Next: <a href="Microsoft-Windows-Variable-Attributes.html#Microsoft-Windows-Variable-Attributes" accesskey="n" rel="next">Microsoft Windows Variable Attributes</a>, Previous: <a href="M32R_002fD-Variable-Attributes.html#M32R_002fD-Variable-Attributes" accesskey="p" rel="prev">M32R/D Variable Attributes</a>, Up: <a href="Variable-Attributes.html#Variable-Attributes" accesskey="u" rel="up">Variable Attributes</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
</div>
|
|
|
|
</body>
|
</html>
|
