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<title>Microcontroller Power Management</title>
<meta name="author" content="Robert Szewczyk, Philip Levis, Martin Turon, Lama Nachman, Philip Buonadonna, Vlado Handziski" />
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+<div class="document" id="microcontroller-power-management">
<h1 class="title">Microcontroller Power Management</h1>
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-<div class="document" id="microcontroller-power-management">
<div class="note">
<p class="first admonition-title">Note</p>
<p class="last">This memo documents a part of TinyOS for the TinyOS Community, and
of this memo is unlimited. This memo is in full compliance with
TEP 1.</p>
</div>
-<div class="section" id="abstract">
-<h1><a name="abstract">Abstract</a></h1>
+<div class="section">
+<h1><a id="abstract" name="abstract">Abstract</a></h1>
<p>This memo documents how TinyOS manages the lower power state of a
microcontroller.</p>
</div>
-<div class="section" id="introduction">
-<h1><a name="introduction">1. Introduction</a></h1>
+<div class="section">
+<h1><a id="introduction" name="introduction">1. Introduction</a></h1>
<p>Microcontrollers often have several power states, with varying power
draws, wakeup latencies, and peripheral support. The microcontroller
should always be in the lowest possible power state that can satisfy
and how they work, as well as the basics of subsystem power
management.</p>
</div>
-<div class="section" id="background">
-<h1><a name="background">2. Background</a></h1>
+<div class="section">
+<h1><a id="background" name="background">2. Background</a></h1>
<p>The TinyOS scheduler[<a class="reference" href="#id3">2</a>] puts a processor into a sleep state when
the task queue is empty. However, processors can have a spectrum of
power states. For example, the MSP430 has one active mode (issuing
requirements, which it considers when calculating the right low power
state.</p>
</div>
-<div class="section" id="id1">
-<h1><a name="id1">3. Microcontroller Power Management</a></h1>
+<div class="section">
+<h1><a id="id1" name="id1">3. Microcontroller Power Management</a></h1>
<p>TinyOS 2.x uses three basic mechanisms to manage and control
microcontroller power states: a dirty bit, a chip-specific low power
state calculation function, and a power state override function. The
</div>
<p>McuSleepC MAY have additional interfaces.</p>
</div>
-<div class="section" id="the-dirty-bit">
-<h1><a name="the-dirty-bit">3.1 The Dirty Bit</a></h1>
+<div class="section">
+<h1><a id="the-dirty-bit" name="the-dirty-bit">3.1 The Dirty Bit</a></h1>
<p>Whenever a Hardware Presentation Layer (HPL, see TEP 2: Hardware
Abstraction Architecture[<a class="reference" href="#id2">1</a>]) component changes an aspect of
hardware configuration that might change the possible low power state
low power state before the next time it goes to sleep as a result of
McuSleep.sleep() being called.</p>
</div>
-<div class="section" id="low-power-state-calculation">
-<h1><a name="low-power-state-calculation">3.2 Low Power State Calculation</a></h1>
+<div class="section">
+<h1><a id="low-power-state-calculation" name="low-power-state-calculation">3.2 Low Power State Calculation</a></h1>
<p>McuSleepC is responsible for calculating the lowest power state that
it can safely put the microcontroller into without disrupting the
operation of TinyOS subsystems. McuSleepC SHOULD minimize how often it
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-<div class="section" id="power-state-override">
-<h1><a name="power-state-override">3.3 Power State Override</a></h1>
+<div class="section">
+<h1><a id="power-state-override" name="power-state-override">3.3 Power State Override</a></h1>
<p>When McuSleepC computes the best low power state, it MUST call
<tt class="docutils literal"><span class="pre">PowerOverride.lowestState().</span></tt> McuSleepC SHOULD have a default
implementation of this command, which returns the lowest power state
<p>Section 5 describes one example use of McuPowerOverride, in the
timer stack for the Atmega128 microcontroller family.</p>
</div>
-<div class="section" id="peripherals-and-subsystems">
-<h1><a name="peripherals-and-subsystems">4. Peripherals and Subsystems</a></h1>
+<div class="section">
+<h1><a id="peripherals-and-subsystems" name="peripherals-and-subsystems">4. Peripherals and Subsystems</a></h1>
<p>At the HIL level, TinyOS subsystems generally have a simple,
imperative power management interface. Depending on the latencies
involved, this interface is either <tt class="docutils literal"><span class="pre">StdControl</span></tt>, <tt class="docutils literal"><span class="pre">SplitControl</span></tt>,
disabled). Following the requirements in 3.1, the MCU power management
subsystem will be notified of a significant change and act
appropriately when the system next goes to sleep. TEP 115[<a class="reference" href="#id6">5</a>]
-describes the power management of non-virtualized devices in
+describes the power management of non-virtualized devices in
greater detail, and TEP 108[<a class="reference" href="#id5">4</a>] describes how TinyOS can automatically
include power management into shared non-virtualized devices.</p>
</div>
-<div class="section" id="implementation">
-<h1><a name="implementation">5. Implementation</a></h1>
-<p>An implementation of McuSleepC can be found in <tt class="docutils literal"><span class="pre">tinyos-2.x/tos/chips/atm128</span></tt>,
+<div class="section">
+<h1><a id="implementation" name="implementation">5. Implementation</a></h1>
+<p>An implementation of McuSleepC can be found in <tt class="docutils literal"><span class="pre">tinyos-2.x/tos/chips/atm128</span></tt>,
<tt class="docutils literal"><span class="pre">tinyos-2.x/tos/chips/msp430</span></tt>, and <tt class="docutils literal"><span class="pre">tinyos-2.x/tos/chips/px27ax</span></tt>.</p>
<p>An example of a use of McuPowerOverride can be found in the atmega128 timer
system. Because some low-power states have much longer wakeup latencies than
others, the timer system does not allow long latencies if it has a timer
-that is going to fire soon. The implementation can be found in
+that is going to fire soon. The implementation can be found in
<tt class="docutils literal"><span class="pre">tinyos-2.x/tos/chips/atm128/timer/HplAtm128Timer0AsyncP.nc</span></tt>, and
<tt class="docutils literal"><span class="pre">tinyos-2.x/tos/chips/atm128/timer/HplAtm128Timer0AsyncC.nc</span></tt> automatically
wires it to McuSleepC if it is included.</p>
</div>
-<div class="section" id="author-s-address">
-<h1><a name="author-s-address">6. Author's Address</a></h1>
+<div class="section">
+<h1><a id="author-s-address" name="author-s-address">6. Author's Address</a></h1>
<div class="line-block">
<div class="line">Robert Szewczyk</div>
<div class="line">Moteiv Corporation</div>
<div class="line"><br /></div>
</div>
</div>
-<div class="section" id="citations">
-<h1><a name="citations">6. Citations</a></h1>
+<div class="section">
+<h1><a id="citations" name="citations">6. Citations</a></h1>
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