Add support for custom system timer frequency

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@274 42af7a65-404d-4744-a932-0658087f49c3

Documentation/NuttX.html

@@ -8,7 +8,7 @@
   <tr align="center" bgcolor="#e4e4e4">
     <td>
       <h1><big><font color="#3c34ec"><i>NuttX RTOS</i></font></big></h1>
-      <p>Last Updated: May 26, 2007</p>
+      <p>Last Updated: June 9, 2007</p>
     </td>
   </tr>
 </table>
@@ -595,7 +595,9 @@ Other memory:
 	* sched/usleep.c: Fixed nsec calculation
 	* lib/lib_strcspn.c: Function incorrectly named strspn().
 	* examples/ostest/main.c:  Errors in SDCC version of a memcpy() call
-	* examples/ostest/sighandl.c: Don't call fflush() if streams are disabled
+	* examples/ostest/sighand.c: Don't call fflush() if streams are disabled
+	* include/limits.h, include/time.h, sched/clock_internal.h: A support for
+	  using selectable system timer frequency.
 	* Started m68322
 </pre></ul>
 

Documentation/NuttxPortingGuide.html

@@ -1163,6 +1163,12 @@ The system can be re-made subsequently by just typing <code>make</code>.
     number of memory regions that the memory manager must
     handle and enables the API mm_addregion(start, end);
   </li>
+  <li>
+    <code>CONFIG_TICKS_PER_MSEC</code>: The default system timer is 100Hz
+    or <code>TICKS_PER_MSEC</code>=10.  This setting may be defined to inform NuttX
+    that the processor hardware is providing system timer interrupts at some interrupt
+    interval other than 10 msec.
+  </li>
   <li>
     <code>CONFIG_RR_INTERVAL</code>: The round robin timeslice will be set
     this number of milliseconds;  Round robin scheduling can