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<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">6.32.8 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>
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<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>
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