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More timer changes from Uros

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3572 42af7a65-404d-4744-a932-0658087f49c3
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patacongo 2011-05-06 21:10:00 +00:00
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Documentation/NuttxPortingGuide.html
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@ -91,7 +91,8 @@
<a href="#updisableirq">4.1.16 <code>up_disable_irq()</code></a><br>
<a href="#upenableirq">4.1.17 <code>up_enable_irq()</code></a><br>
<a href="#upprioritizeirq">4.1.18 <code>up_prioritize_irq()</code></a></br>
<a href="#upputc">4.1.19 <code>up_putc()</code></a>
<a href="#upputc">4.1.19 <code>up_putc()</code></a></br>
<a href="#systemtime">4.1.20 System Time and Clock</a>
</ul>
<a href="#exports">4.2 APIs Exported by NuttX to Architecture-Specific Logic</a>
<ul>
@ -1642,6 +1643,90 @@ The system can be re-made subsequently by just typing <code>make</code>.
Output one character on the console
</p>
<h3><a name="systemtime">4.1.20 System Time and Clock</a></h3>
<h4>4.1.20.1 UTC Time Representation</h4>
<p>
To enable UTC time representation use option:
</p>
<ul><pre>
CONFIG_SYSTEM_UTC=y
</pre></ul>
<p>
which adds the following variables:
</p>
<ul>
<li><code>g_system_utc</code> (seconds, 4 bytes)</li>
<li><code>g_tickcount</code> (timer ticks, 1-2 bytes typically)</li>
</ul>
<p>
and replaces:
</p>
<ul>
<li><code>g_system_timer</code>(4 bytes)</li>
<li><code>g_basetime</code>(8 bytes)</li>
<li><code>g_tickbias</code>(4 bytes)</li>
</ul>
<p>
Otherwise internal time is computed from 32-bit running tick timer
<code>g_systemtimer</code> the start date <code>g_basetime</code> and time offset the <code>g_tickbias</code>.
</p>
<h4>4.1.20.2 Hardware</h4>
<p>
To enable hardware module use option:
<p>
<ul><pre>
CONFIG_RTC=y
</pre></ul>
<p>
which requires the following three base functions to read time:
</p>
<ul>
<li><code>up_rtcinitialize()</code></li>
<li><code>up_rtc_gettime()</code>. UTC time in seconds.</li>
<li><code>up_rtc_getclock()</code>. Replacement for <code>g_system_tick</code></li>
</ul>
<p>
This module depends on <code>CONFIG_SYSTEM_UTC=y</code>.
</p>
<h4>4.1.20.3 System Tick and Time</h4>
<p>
The system tick is represented by, when <code>CONFIG_SYSTEM_UTC=n</code>:
</p>
<ul>
<li><code>g_system_timer</code></li>
</ul>
<p>
or, when <code>CONFIG_SYSTEM_UTC=y</code>
</p>
<ul>
<li><code>g_tickcount</code></li>
<li><code>g_system_utc</code></li>
</ul>
<p>
Running at rate of system base timer, used for time-slicing, and so forth.
</p>
<p>
If hardware RTC is present (<code>CONFIG_RTC</code>) and enabled, then after successful
initiliazation variables are overriden by calls to <code>up_rtc_getclock()</code> which is
running continously even in power-down modes.
</p>
<p>
In the case of <code>CONFIG_RTC</code> is set the <code>g_tickcount</code> and <code>g_system_utc</code> keep
counting at rate of a system timer, which however, is disabled in power-down
mode. By comparing this time and RTC (actual time) one may determine the
actual system active time. To retrieve that variable use:
</p>
<ul><pre>
<li><code>clock_gettime(CLOCK_ACTIVETIME, tp)</code>
</pre></ul>
<p>
If the <code>CLOCK_ACTIVETIME</code> time is never set it will serve as power-up time
minus all deep sleeps.
</p>
<h2><a name="exports">4.2 APIs Exported by NuttX to Architecture-Specific Logic</a></h2>
<p>
These are standard interfaces that are exported by the OS