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<title>Hardware Abstraction Architecture</title>
<meta name="author" content="Vlado Handziski, Joseph Polastre, Jan-Hinrich Hauer, Cory Sharp, Adam Wolisz, David Culler, David Gay" />
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-<div class="document" id="hardware-abstraction-architecture">
<h1 class="title">Hardware Abstraction Architecture</h1>
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Cory Sharp, Adam Wolisz, David Culler, David Gay</td></tr>
<tr class="field"><th class="docinfo-name">Draft-Created:</th><td class="field-body">14-Sep-2004</td>
</tr>
-<tr class="field"><th class="docinfo-name">Draft-Version:</th><td class="field-body">1.5</td>
+<tr class="field"><th class="docinfo-name">Draft-Version:</th><td class="field-body">1.6</td>
</tr>
<tr class="field"><th class="docinfo-name">Draft-Modified:</th><td class="field-body">2007-02-28</td>
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+<div class="document" id="hardware-abstraction-architecture">
<div class="note">
<p class="first admonition-title">Note</p>
<p class="last">This document specifies a Best Current Practices for the TinyOS
under IEEE copyright and from the <a class="citation-reference" href="#t2-tr" id="id2" name="id2">[T2_TR]</a> technical report. This
memo is in full compliance with <a class="citation-reference" href="#tep1" id="id3" name="id3">[TEP1]</a>.</p>
</div>
-<div class="section">
-<h1><a id="abstract" name="abstract">Abstract</a></h1>
+<div class="section" id="abstract">
+<h1><a name="abstract">Abstract</a></h1>
<p>This TEP documents a <em>Hardware Abstraction Architecture (HAA)</em> for
TinyOS 2.0 that balances the conflicting requirements of code
reusability and portability on the one hand and efficiency and
exported at the second layer, when the performance requirements
outweigh the need for cross-platform compatibility.</p>
</div>
-<div class="section">
-<h1><a id="introduction" name="introduction">1. Introduction</a></h1>
+<div class="section" id="introduction">
+<h1><a name="introduction">1. Introduction</a></h1>
<p>The introduction of hardware abstraction in operating systems has
proved valuable for increasing portability and simplifying application
development by hiding the hardware intricacies from the rest of the
focus on the hardware abstraction for a particular hardware module,
and <a class="citation-reference" href="#tep112" id="id7" name="id7">[TEP112]</a> and <a class="citation-reference" href="#tep115" id="id8" name="id8">[TEP115]</a> explain how power management is realized.</p>
</div>
-<div class="section">
-<h1><a id="architecture" name="architecture">2. Architecture</a></h1>
+<div class="section" id="architecture">
+<h1><a name="architecture">2. Architecture</a></h1>
<p>In the proposed architecture (<a class="reference" href="#fig-1">Fig.1</a>), the hardware abstraction
functionality is organized in three distinct layers of components.
Each layer has clearly defined responsibilities and is dependent on
the components become less and less hardware dependent, giving the
developer more freedom in the design and the implementation of
reusable applications.</p>
-<pre class="literal-block" id="fig-1">
+<a class="target" id="fig-1" name="fig-1"></a><pre class="literal-block">
+-----------------------------+
| |
| Cross-platform applications |
capabilities of the hardware module.</p>
<p>The rest of the section discusses the specific roles of each component
layer in more detail.</p>
-<div class="section">
-<h2><a id="hardware-presentation-layer-hpl" name="hardware-presentation-layer-hpl">Hardware Presentation Layer (HPL)</a></h2>
+<div class="section" id="hardware-presentation-layer-hpl">
+<h2><a name="hardware-presentation-layer-hpl">Hardware Presentation Layer (HPL)</a></h2>
<p>The components belonging to the <em>HPL</em> are positioned directly over the
HW/SW interface. As the name suggests, their major task is to
"present" the capabilities of the hardware using the native concepts
(<em>not</em> rewriting) the <em>HPL</em> components, without any changes to the
implementation code.</p>
</div>
-<div class="section">
-<h2><a id="hardware-adaptation-layer-hal" name="hardware-adaptation-layer-hal">Hardware Adaptation Layer (HAL)</a></h2>
+<div class="section" id="hardware-adaptation-layer-hal">
+<h2><a name="hardware-adaptation-layer-hal">Hardware Adaptation Layer (HAL)</a></h2>
<p>The adaptation layer components represent the core of the
architecture. They use the raw interfaces provided by the <em>HPL</em>
components to build useful abstractions hiding the complexity
behind few overloaded commands. This also enables more efficient
compile-time detection of abstraction interface usage errors.</p>
</div>
-<div class="section">
-<h2><a id="hardware-interface-layer-hil" name="hardware-interface-layer-hil">Hardware Interface Layer (HIL)</a></h2>
+<div class="section" id="hardware-interface-layer-hil">
+<h2><a name="hardware-interface-layer-hil">Hardware Interface Layer (HIL)</a></h2>
<p>The final tier in the architecture is formed by the <em>HIL</em> components
that take the platform-specific abstractions provided by the <em>HAL</em> and
convert them to hardware-independent interfaces used by cross-platform
increasing levels of functionality.</p>
</div>
</div>
-<div class="section">
-<h1><a id="combining-different-levels-of-abstraction" name="combining-different-levels-of-abstraction">3. Combining different levels of abstraction</a></h1>
+<div class="section" id="combining-different-levels-of-abstraction">
+<h1><a name="combining-different-levels-of-abstraction">3. Combining different levels of abstraction</a></h1>
<p>Providing two levels of abstraction to the application --the <em>HIL</em> and
<em>HAL</em>-- means that a hardware asset may be accessed at two levels in
parallel, e.g. from different parts of the application and the OS
interface of the <em>HAL</em> component as it provides much finer control
over the conversion process. (<a class="reference" href="#fig-2">Fig.2</a>) depicts how the ADC hardware
stack on the MSP430 MCU on the level of <em>HIL</em> and <em>HAL</em> in parallel.</p>
-<pre class="literal-block" id="fig-2">
+<a class="target" id="fig-2" name="fig-2"></a><pre class="literal-block">
+--------------------------------+
| APP |
+-+----------------------------+-+
so that a safe shared access to the <em>HPL</em> exported resources can be
guaranteed.</p>
</div>
-<div class="section">
-<h1><a id="horizontal-decomposition" name="horizontal-decomposition">4. Horizontal decomposition</a></h1>
+<div class="section" id="horizontal-decomposition">
+<h1><a name="horizontal-decomposition">4. Horizontal decomposition</a></h1>
<p>In addition to the <em>vertical</em> decomposition of the <em>HAA</em>, a
<em>horizontal</em> decomposition can promote reuse of the hardware resource
abstractions that are common on different platforms. To this aim,
providing <em>HIL</em> implementation(s) as the topmost component(s).
Platforms are then built as compositions of different chip components
with the help of "glue" components that perform the mapping (<a class="reference" href="#fig-3">Fig.3</a>)</p>
-<pre class="literal-block" id="fig-3">
+<a class="target" id="fig-3" name="fig-3"></a><pre class="literal-block">
+----------------------------------------------------+
| AppC |
| /Application Component/ |
both in dedicated scenarios, as well as in situations where multiple
chips are connected to the same physical bus interconnect.</p>
</div>
-<div class="section">
-<h1><a id="cpu-abstraction" name="cpu-abstraction">5. CPU abstraction</a></h1>
+<div class="section" id="cpu-abstraction">
+<h1><a name="cpu-abstraction">5. CPU abstraction</a></h1>
<p>In TinyOS most of the variability between the processing units is
hidden from the OS simply by using a nesC/C based programming language
with a common compiler suite (GCC). For example, the standard library
of the hardware abstraction functionality will have to be explicitly
addressed.</p>
</div>
-<div class="section">
-<h1><a id="hil-alignment" name="hil-alignment">6. HIL alignment</a></h1>
+<div class="section" id="hil-alignment">
+<h1><a name="hil-alignment">6. HIL alignment</a></h1>
<p>While the <em>HAA</em> requires that the <em>HIL</em> provides full hardware
independence (<a class="reference" href="#strong-real-hils">Strong/Real HILs</a>), some abstractions might only
partially meet this goal (<a class="reference" href="#weak-hils">Weak HILs</a>). This section introduces
definition may be different</li>
<li><em>platform-specific X:</em> X is defined on just one platform</li>
</ul>
-<div class="section">
-<h2><a id="strong-real-hils" name="strong-real-hils">Strong/Real HILs</a></h2>
+<div class="section" id="strong-real-hils">
+<h2><a name="strong-real-hils">Strong/Real HILs</a></h2>
<p><em>Strong/Real HILs</em> mean that "code using these abstractions can
reasonably be expected to behave the same on all implementations".
This matches the original definition of the <em>HIL</em> level according to
example, the TinyOS 2.x message buffer abstraction, <tt class="docutils literal"><span class="pre">message_t</span></tt>
(<a class="citation-reference" href="#tep111" id="id17" name="id17">[TEP111]</a>).</p>
</div>
-<div class="section">
-<h2><a id="weak-hils" name="weak-hils">Weak HILs</a></h2>
+<div class="section" id="weak-hils">
+<h2><a name="weak-hils">Weak HILs</a></h2>
<p><em>Weak HILs</em> mean that one "can write portable code over these
abstractions, but any use of them involves platform-specific
behavior". Although such platform-specific behavior can --at least at
which should help programmers and provide guidance to platform
developers.</p>
</div>
-<div class="section">
-<h2><a id="hardware-independent-interfaces-hii" name="hardware-independent-interfaces-hii">Hardware Independent Interfaces (HII)</a></h2>
+<div class="section" id="hardware-independent-interfaces-hii">
+<h2><a name="hardware-independent-interfaces-hii">Hardware Independent Interfaces (HII)</a></h2>
<p><em>Hardware Independent Interfaces (HII)</em>, is just an interface
definition intended for use across multiple platforms.</p>
<p>Examples include the SID interfaces, the pin interfaces from <a class="citation-reference" href="#tep117" id="id18" name="id18">[TEP117]</a>,
the Alarm/Counter/etc interfaces from <a class="citation-reference" href="#tep102" id="id19" name="id19">[TEP102]</a>.</p>
</div>
-<div class="section">
-<h2><a id="utility-components" name="utility-components">Utility components</a></h2>
+<div class="section" id="utility-components">
+<h2><a name="utility-components">Utility components</a></h2>
<p><em>Utility components</em> are pieces of clearly portable code (typically
generic components), which aren't exposing a self-contained service.
Examples include the components in tos/lib/timer and the
ArbitratedRead* components. These provide and use HIIs.</p>
</div>
</div>
-<div class="section">
-<h1><a id="conclusion" name="conclusion">6. Conclusion</a></h1>
+<div class="section" id="conclusion">
+<h1><a name="conclusion">6. Conclusion</a></h1>
<p>The proposed hardware abstraction architecture provides a set of core
services that eliminate duplicated code and provide a coherent view of
the system across different platforms. It supports the concurrent use
while using standard cross-platform hardware interfaces for the
remainder of the application.</p>
</div>
-<div class="section">
-<h1><a id="author-s-address" name="author-s-address">Author's Address</a></h1>
+<div class="section" id="author-s-address">
+<h1><a name="author-s-address">Author's Address</a></h1>
<div class="line-block">
<div class="line">Vlado Handziski (handzisk at tkn.tu-berlin.de) <a class="footnote-reference" href="#id27" id="id20" name="id20">[1]</a> </div>
<div class="line">Joseph Polastre (polastre at cs.berkeley.edu) <a class="footnote-reference" href="#id28" id="id21" name="id21">[2]</a> </div>
</tbody>
</table>
</div>
-<div class="section">
-<h1><a id="citations" name="citations">Citations</a></h1>
+<div class="section" id="citations">
+<h1><a name="citations">Citations</a></h1>
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projects / tinyos-2.x.git / blobdiff