1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>Chapter&#160;4.&#160;Port Space Accesses</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="Bus-Independent Device Accesses"><link rel="up" href="index.html" title="Bus-Independent Device Accesses"><link rel="prev" href="accessing_the_device.html" title="Accessing the device"><link rel="next" href="accessing_port_space.html" title="Accessing Port Space"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter&#160;4.&#160;Port Space Accesses</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="accessing_the_device.html">Prev</a>&#160;</td><th width="60%" align="center">&#160;</th><td width="20%" align="right">&#160;<a accesskey="n" href="accessing_port_space.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="port_space_accesses"></a>Chapter&#160;4.&#160;Port Space Accesses</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="sect1"><a href="port_space_accesses.html#port_space_explained">Port Space Explained</a></span></dt><dt><span class="sect1"><a href="accessing_port_space.html">Accessing Port Space</a></span></dt></dl></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="port_space_explained"></a>Port Space Explained</h2></div></div></div><p>
2	Another form of IO commonly supported is Port Space.  This is a
3	range of addresses separate to the normal memory address space.
4	Access to these addresses is generally not as fast as accesses
5	to the memory mapped addresses, and it also has a potentially
6	smaller address space.
7      </p><p>
8	Unlike memory mapped IO, no preparation is required
9	to access port space.
10      </p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="accessing_the_device.html">Prev</a>&#160;</td><td width="20%" align="center">&#160;</td><td width="40%" align="right">&#160;<a accesskey="n" href="accessing_port_space.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Accessing the device&#160;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&#160;Accessing Port Space</td></tr></table></div></body></html>
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