timing.html
来自「A tutorial on RT-Linux」· HTML 代码 · 共 268 行
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<HTML><HEAD> <TITLE>RTAI 1.0 documentation - Timer functions</TITLE> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <META NAME="Generator" CONTENT="VIM - Vi IMproved 5.3"></HEAD><BODY><A NAME="rt_set_oneshot_mode"></a><A NAME="rt_set_periodic_mode"></a><dl><dt><H3>NAME</H3></dt><dd>rt_set_oneshot_mode, rt_set_periodic_mode - set timer mode</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_sched.h"<p><B>void rt_set_oneshot_mode (void);</B><p><B>void rt_set_periodic_mode (void);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>rt_set_oneshot_mode</b> sets the oneshot mode for the timer.It consists in a variable timing based on the cpu clock frequency.This allows task to be timed arbitrarily. It must be called beforeusing any time related function, including conversions.<p><b>rt_set_periodic_mode</b> sets the periodic mode for the timer.It consists of a fixed frequency timing of the tasks in multiple ofthe period set with a call to <b>start_rt_timer</b>. The resolutionis that of the 8254 frequency (1193180 hz). Any timing request not an integermultiple of the period is satisfied at the closest period tick. It is thedefault mode when no call is made to set the oneshot mode.<p>Oneshot mode can be set initially also with <b>OneShot</b>command line parameter of the <b>rtai_sched</b> module.</dd></dl><dl><dt><H3>NOTE</H3></dt><dd>Stopping the timer by <b>stop_rt_timer</b> sets the timer backinto its defult (periodic) mode.Call <b>rt_set_oneshot_mode</b> before each <b>start_rt_timer</b>if it required.</dd></dl><p align=right><A HREF="manual.html#timing">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="start_rt_timer"></A><dl><dt><H3>NAME</H3></dt><dd>start_rt_timer, stop_rt_timer - start/stop timer</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_sched.h"<p><B>RTIME start_rt_timer (int </B><I>period</I><B>);</B><p><B>void stop_rt_timer (void);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>start_rt_timer</b> starts the timer with a period <I>period.</I>The period is in internal count units and is requiredonly for the periodic mode. In the oneshot the parameter value is ignored.<p><b>stop_rt_timer</b> stops the timer. The timer mode is set to periodic.</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>The period in internal count units.</dd></dl><p align=right><A HREF="manual.html#timing">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="count2nano"></A><A NAME="nano2count"></A><dl><dt><H3>NAME</H3></dt><dd>count2nano, nano2count - convert internal count units to nanosecs and back</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_sched.h"<p><B>RTIME count2nano (RTIME </B><I>timercounts</I>)<B>;</B><p><B>RTIME nano2count (RTIME </B><I>nanosecs</I><B>);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>count2nano</b> converts the time of <I>timercounts</I> internalcount units into nanoseconds.<p><b>nano2count</b> converts the time of <i>nanosecs</i> nanosecondsinto internal counts units.<p>Remember that the count units are related to the cpu frequency inoneshot mode and to the 8254 frequency (1193180 Hz) in periodic mode.</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>The given time in nanoseconds/internal count units is returned.</dd></dl><p align=right><A HREF="manual.html#timing">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="rt_get_time"></A><A NAME="rt_get_time_ns"></A><A NAME="rt_get_cpu_time_ns"></A><dl><dt><H3>NAME</H3></dt><dd>rt_get_time, rt_get_time_ns, rt_get_cpu_time_ns - get the current time</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_sched.h"<p><B>RTIME rt_get_time (void);</B><p><B>RTIME rt_get_time_ns (void);</B><p><B>RTIME rt_get_cpu_time_ns (void);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>rt_get_time</b> returns the number of real time clock ticks since RT_TIMERbootup (<i>whatever this means</i>).This number is multiple of the 8254 period in periodic mode, whileis multiple of cpu clock period in oneshot mode.<p><b>rt_get_time_ns</b> is the same as <b>rt_get_time</b> but the returned timeis converted to nanoseconds.<p><b>rt_get_cpu_time_ns</b> ???</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>The current time in internal count units/nanoseconds is returned.</dd></dl><p align=right><A HREF="manual.html#timing">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="next_period"></A><dl><dt><H3>NAME</H3></dt><dd>next_period - get the time of next run</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_sched.h"<p><B>RTIME next_period (void);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>next_period</b> returns the time when the caller task will run next.</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>Next period time in internal count units.</dd></dl><p align=right><A HREF="manual.html#timing">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="rt_busy_sleep"></A><A NAME="rt_sleep"></A><A NAME="rt_sleep_until"></A><dl><dt><H3>NAME</H3></dt><dd>rt_busy_sleep, rt_sleep, rt_sleep_until - delay/suspend execution for a while</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_sched.h"<p><B>void rt_busy_sleep (int </B><I>nanosecs</I><B>);</B><p><B>void rt_sleep (RTIME </B><I>delay</I><B>);</B><p><B>void rt_sleep_until (RTIME </B><I>time</I><B>);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>rt_busy_sleep</b> delays the execution of the caller taskwithout giving back the control to the scheduler.This function burns away CPU cycles in a busy wait loopIt may be used for very short synchronization delays only.<br><I>nanosecs</I> is the number of nanoseconds to wait.<p><b>rt_sleep</b> suspends execution of the caller task for atime of <I>delay</I> internal count units. During this time theCPU is used by other tasks.<p><b>rt_sleep_until</b> is similar to <b>rt_sleep</b> but theparameter <I>time</I> is the absolute time till the task have tobe suspended. If the given time is already passed this call has no effect.<p>Note: a higher priority task or interrupt handler can run during waitso the actual time spent in these functions may be longerthan the specified.</dd></dl><dl><dt><H3>NOTE</H3></dt><dd>A higher priority task or interrupt handler can run during waitso the actual time spent in these functions may be longerthan the specified.</dd></dl><p align=right><A HREF="manual.html#timing">[return to index]</A></p></BODY></HTML>⌨️ 快捷键说明
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