OpenCores
URL https://opencores.org/ocsvn/openrisc/openrisc/trunk

Subversion Repositories openrisc

[/] [openrisc/] [trunk/] [rtos/] [ecos-2.0/] [doc/] [html/] [ref/] [kernel-alarms.html] - Blame information for rev 611

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 28 unneback 
<!-- Copyright (C) 2003 Red Hat, Inc.                                -->
2 
<!-- This material may be distributed only subject to the terms      -->
3 
<!-- and conditions set forth in the Open Publication License, v1.0  -->
4 
<!-- or later (the latest version is presently available at          -->
5 
<!-- http://www.opencontent.org/openpub/).                           -->
6 
<!-- Distribution of the work or derivative of the work in any       -->
7 
<!-- standard (paper) book form is prohibited unless prior           -->
8 
<!-- permission is obtained from the copyright holder.               -->
9 
<HTML
10 
><HEAD
11 
><TITLE
12 
>Alarms</TITLE
13 
><meta name="MSSmartTagsPreventParsing" content="TRUE">
14 
<META
15 
NAME="GENERATOR"
16 
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
17 
"><LINK
18 
REL="HOME"
19 
TITLE="eCos Reference Manual"
20 
HREF="ecos-ref.html"><LINK
21 
REL="UP"
22 
TITLE="The eCos Kernel"
23 
HREF="kernel.html"><LINK
24 
REL="PREVIOUS"
25 
TITLE="Clocks"
26 
HREF="kernel-clocks.html"><LINK
27 
REL="NEXT"
28 
TITLE="Mutexes"
29 
HREF="kernel-mutexes.html"></HEAD
30 
><BODY
31 
CLASS="REFENTRY"
32 
BGCOLOR="#FFFFFF"
33 
TEXT="#000000"
34 
LINK="#0000FF"
35 
VLINK="#840084"
36 
ALINK="#0000FF"
37 
><DIV
38 
CLASS="NAVHEADER"
39 
><TABLE
40 
SUMMARY="Header navigation table"
41 
WIDTH="100%"
42 
BORDER="0"
43 
CELLPADDING="0"
44 
CELLSPACING="0"
45 
><TR
46 
><TH
47 
COLSPAN="3"
48 
ALIGN="center"
49 
>eCos Reference Manual</TH
50 
></TR
51 
><TR
52 
><TD
53 
WIDTH="10%"
54 
ALIGN="left"
55 
VALIGN="bottom"
56 
><A
57 
HREF="kernel-clocks.html"
58 
ACCESSKEY="P"
59 
>Prev</A
60 
></TD
61 
><TD
62 
WIDTH="80%"
63 
ALIGN="center"
64 
VALIGN="bottom"
65 
></TD
66 
><TD
67 
WIDTH="10%"
68 
ALIGN="right"
69 
VALIGN="bottom"
70 
><A
71 
HREF="kernel-mutexes.html"
72 
ACCESSKEY="N"
73 
>Next</A
74 
></TD
75 
></TR
76 
></TABLE
77 
><HR
78 
ALIGN="LEFT"
79 
WIDTH="100%"></DIV
80 
><H1
81 
><A
82 
NAME="KERNEL-ALARMS">Alarms</H1
83 
><DIV
84 
CLASS="REFNAMEDIV"
85 
><A
86 
NAME="AEN1016"
87 
></A
88 
><H2
89 
>Name</H2
90 
>cyg_alarm_create, cyg_alarm_delete, cyg_alarm_initialize, cyg_alarm_enable, cyg_alarm_disable&nbsp;--&nbsp;Run an alarm function when a number of events have occurred</DIV
91 
><DIV
92 
CLASS="REFSYNOPSISDIV"
93 
><A
94 
NAME="AEN1023"><H2
95 
>Synopsis</H2
96 
><DIV
97 
CLASS="FUNCSYNOPSIS"
98 
><A
99 
NAME="AEN1024"><P
100 
></P
101 
><TABLE
102 
BORDER="5"
103 
BGCOLOR="#E0E0F0"
104 
WIDTH="70%"
105 
><TR
106 
><TD
107 
><PRE
108 
CLASS="FUNCSYNOPSISINFO"
109 
>#include &lt;cyg/kernel/kapi.h&gt;
110 
        </PRE
111 
></TD
112 
></TR
113 
></TABLE
114 
><P
115 
><CODE
116 
><CODE
117 
CLASS="FUNCDEF"
118 
>void cyg_alarm_create</CODE
119 
>(cyg_handle_t counter, cyg_alarm_t* alarmfn, cyg_addrword_t data, cyg_handle_t* handle, cyg_alarm* alarm);</CODE
120 
></P
121 
><P
122 
><CODE
123 
><CODE
124 
CLASS="FUNCDEF"
125 
>void cyg_alarm_delete</CODE
126 
>(cyg_handle_t alarm);</CODE
127 
></P
128 
><P
129 
><CODE
130 
><CODE
131 
CLASS="FUNCDEF"
132 
>void cyg_alarm_initialize</CODE
133 
>(cyg_handle_t alarm, cyg_tick_count_t trigger, cyg_tick_count_t interval);</CODE
134 
></P
135 
><P
136 
><CODE
137 
><CODE
138 
CLASS="FUNCDEF"
139 
>void cyg_alarm_enable</CODE
140 
>(cyg_handle_t alarm);</CODE
141 
></P
142 
><P
143 
><CODE
144 
><CODE
145 
CLASS="FUNCDEF"
146 
>void cyg_alarm_disable</CODE
147 
>(cyg_handle_t alarm);</CODE
148 
></P
149 
><P
150 
></P
151 
></DIV
152 
></DIV
153 
><DIV
154 
CLASS="REFSECT1"
155 
><A
156 
NAME="KERNEL-ALARMS-DESCRIPTION"
157 
></A
158 
><H2
159 
>Description</H2
160 
><P
161 
>Kernel alarms are used together with counters and allow for action to
162 
be taken when a certain number of events have occurred. If the counter
163 
is associated with a clock then the alarm action happens when the
164 
appropriate number of clock ticks have occurred, in other words after
165 
a certain period of time.
166 
      </P
167 
><P
168 
>Setting up an alarm involves a two-step process. First the alarm must
169 
be created with a call to <TT
170 
CLASS="FUNCTION"
171 
>cyg_alarm_create</TT
172 
>. This
173 
takes five arguments. The first identifies the counter to which the
174 
alarm should be attached. If the alarm should be attached to the
175 
system's real-time clock then <TT
176 
CLASS="FUNCTION"
177 
>cyg_real_time_clock</TT
178 
>
179 
and <TT
180 
CLASS="FUNCTION"
181 
>cyg_clock_to_counter</TT
182 
> can be used to get hold
183 
of the appropriate handle. The next two arguments specify the action
184 
to be taken when the alarm is triggered, in the form of a function
185 
pointer and some data. This function should take the form:
186 
      </P
187 
><TABLE
188 
BORDER="5"
189 
BGCOLOR="#E0E0F0"
190 
WIDTH="70%"
191 
><TR
192 
><TD
193 
><PRE
194 
CLASS="PROGRAMLISTING"
195 
>void
196 
alarm_handler(cyg_handle_t alarm, cyg_addrword_t data)
197 
{
198 
    &#8230;
199 
}
200 
      </PRE
201 
></TD
202 
></TR
203 
></TABLE
204 
><P
205 
>The data argument passed to the alarm function corresponds to the
206 
third argument passed to <TT
207 
CLASS="FUNCTION"
208 
>cyg_alarm_create</TT
209 
>.
210 
The fourth argument to <TT
211 
CLASS="FUNCTION"
212 
>cyg_alarm_create</TT
213 
> is used
214 
to return a handle to the newly-created alarm object, and the final
215 
argument provides the memory needed for the alarm object and thus
216 
avoids any need for dynamic memory allocation within the kernel.
217 
      </P
218 
><P
219 
>Once an alarm has been created a further call to
220 
<TT
221 
CLASS="FUNCTION"
222 
>cyg_alarm_initialize</TT
223 
> is needed to activate it.
224 
The first argument specifies the alarm. The second argument indicates
225 
the number of events, for example clock ticks, that need to occur
226 
before the alarm triggers. If the third argument is 0 then the alarm
227 
will only trigger once. A non-zero value specifies that the alarm
228 
should trigger repeatedly, with an interval of the specified number of
229 
events.
230 
      </P
231 
><P
232 
>Alarms can be temporarily disabled and reenabled using
233 
<TT
234 
CLASS="FUNCTION"
235 
>cyg_alarm_disable</TT
236 
> and
237 
<TT
238 
CLASS="FUNCTION"
239 
>cyg_alarm_enable</TT
240 
>. Alternatively another call to
241 
<TT
242 
CLASS="FUNCTION"
243 
>cyg_alarm_initialize</TT
244 
> can be used to modify the
245 
behaviour of an existing alarm. If an alarm is no longer required then
246 
the associated resources can be released using
247 
<TT
248 
CLASS="FUNCTION"
249 
>cyg_alarm_delete</TT
250 
>.
251 
      </P
252 
><P
253 
>The alarm function is invoked when a counter tick occurs, in other
254 
words when there is a call to <TT
255 
CLASS="FUNCTION"
256 
>cyg_counter_tick</TT
257 
>,
258 
and will happen in the same context. If the alarm is associated with
259 
the system's real-time clock then this will be DSR context, following
260 
a clock interrupt. If the alarm is associated with some other
261 
application-specific counter then the details will depend on how that
262 
counter is updated.
263 
      </P
264 
><P
265 
>If two or more alarms are registered for precisely the same counter tick,
266 
the order of execution of the alarm functions is unspecified.
267 
      </P
268 
></DIV
269 
><DIV
270 
CLASS="REFSECT1"
271 
><A
272 
NAME="KERNEL-ALARMS-CONTEXT"
273 
></A
274 
><H2
275 
>Valid contexts</H2
276 
><P
277 
><TT
278 
CLASS="FUNCTION"
279 
>cyg_alarm_create</TT
280 
>
281 
<TT
282 
CLASS="FUNCTION"
283 
>cyg_alarm_initialize</TT
284 
> is typically called during
285 
system initialization but may also be called in thread context. The
286 
same applies to <TT
287 
CLASS="FUNCTION"
288 
>cyg_alarm_delete</TT
289 
>.
290 
<TT
291 
CLASS="FUNCTION"
292 
>cyg_alarm_initialize</TT
293 
>,
294 
<TT
295 
CLASS="FUNCTION"
296 
>cyg_alarm_disable</TT
297 
> and
298 
<TT
299 
CLASS="FUNCTION"
300 
>cyg_alarm_enable</TT
301 
> may be called during
302 
initialization or from thread or DSR context, but
303 
<TT
304 
CLASS="FUNCTION"
305 
>cyg_alarm_enable</TT
306 
> and
307 
<TT
308 
CLASS="FUNCTION"
309 
>cyg_alarm_initialize</TT
310 
> may be expensive operations
311 
and should only be called when necessary.
312 
      </P
313 
></DIV
314 
><DIV
315 
CLASS="NAVFOOTER"
316 
><HR
317 
ALIGN="LEFT"
318 
WIDTH="100%"><TABLE
319 
SUMMARY="Footer navigation table"
320 
WIDTH="100%"
321 
BORDER="0"
322 
CELLPADDING="0"
323 
CELLSPACING="0"
324 
><TR
325 
><TD
326 
WIDTH="33%"
327 
ALIGN="left"
328 
VALIGN="top"
329 
><A
330 
HREF="kernel-clocks.html"
331 
ACCESSKEY="P"
332 
>Prev</A
333 
></TD
334 
><TD
335 
WIDTH="34%"
336 
ALIGN="center"
337 
VALIGN="top"
338 
><A
339 
HREF="ecos-ref.html"
340 
ACCESSKEY="H"
341 
>Home</A
342 
></TD
343 
><TD
344 
WIDTH="33%"
345 
ALIGN="right"
346 
VALIGN="top"
347 
><A
348 
HREF="kernel-mutexes.html"
349 
ACCESSKEY="N"
350 
>Next</A
351 
></TD
352 
></TR
353 
><TR
354 
><TD
355 
WIDTH="33%"
356 
ALIGN="left"
357 
VALIGN="top"
358 
>Clocks</TD
359 
><TD
360 
WIDTH="34%"
361 
ALIGN="center"
362 
VALIGN="top"
363 
><A
364 
HREF="kernel.html"
365 
ACCESSKEY="U"
366 
>Up</A
367 
></TD
368 
><TD
369 
WIDTH="33%"
370 
ALIGN="right"
371 
VALIGN="top"
372 
>Mutexes</TD
373 
></TR
374 
></TABLE
375 
></DIV
376 
></BODY
377 
></HTML
378 
>

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.