c22.htm
来自「ST20 Embedded Toolset R2.0.5用于开发基于ST20芯片」· HTM 代码 · 共 90 行
HTM
90 行
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<meta name="GENERATOR" content="Quadralay WebWorks Publisher Professional Edition 6.0.5">
<meta name="TEMPLATEBASE" content="book_html">
<meta name="LASTUPDATED" content="12/01/03 14:15:48">
<title>14.1 Overview</title>
<STYLE TYPE="text/css">
<!--
span.Signal { text-transform: uppercase; font-family: Verdana }
-->
</STYLE>
</head>
<body link="#3366CC" vlink="#9999CC" text="#000000" alink="#0000CC" bgcolor="#FFFFFF"
background="images/backgrnd.gif">
<p><img src="images/stlogo.gif" width="106" height="83" align="left"
alt="logo here!"> </p>
<table width="331" border="0" align="right" cellpadding="0" cellspacing="0">
<tr>
<td><a href="os20toc.htm"><img src="images/navtoc.gif" width="84" height="23"
border="0" alt="TOC"> </a></td>
<td><a href="c2.htm"><img src="images/navprev.gif" width="80" height="23"
border="0" alt="PREV"> </a></td>
<td><a href="c23.htm"><img src="images/navnext.gif" width="83" height="23"
border="0" alt="NEXT"> </a></td>
<td><a href="os20ix.htm"><img src="images/navidx.gif" width="84" height="23"
border="0" alt="INDEX"> </a></td>
</tr>
</table>
<p><br clear="all">
</p>
<hr align="left">
<blockquote>
<h2>
<a name="1204412"> </a><font color="#003366" face="Verdana, Arial, Helvetica, sans-serif">14.1 Overview</font>
</h2><hr>
<p>
<a name="1206478"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The ST20C2 has the following additional features over the ST20-C1.</font>
</p>
<ul>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204415"> </a><font face="Verdana, Arial, Helvetica, sans-serif"><b>Channels</b></font></font></p>
<dl>
<dt> <a name="1204416"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The ST20C2 supports a point-to-point unidirectional communications channel, which can be used for communication between tasks on the same processor, and with hardware peripherals on the ST20.</font>
</dl>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204417"> </a><strong>High priority processes</strong></font></p>
<dl>
<dt> <a name="1204421"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">High priority processes run outside of the normal OS20 scheduling regime, using the ST20's hardware scheduler. A high priority process is created using the <font size=2 face=Courier><strong>task_create</strong></font> or <font size=2 face=Courier><strong>task_init</strong></font> functions and specifying the <font size=2 face=Courier><strong>task_flags_high_priority_process</strong></font> flag. High priority processes always preempt normal OS20 tasks (irrespective of the task's priority) and as this takes advantage of the ST20's hardware scheduler, high priority processes can respond faster than normal OS20 tasks.</font>
<dt> <a name="1204430"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">In general, high priority processes should be regarded as the equivalent of interrupt handlers for those peripherals which have a channel style interface.</font>
<dt> <a name="1204444"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">However, because high priority processes run outside of the OS20 scheduling regime, they only have very limited access to OS20 library functions. In general they can only call functions which are implemented directly in hardware; in particular, this means they can only use channels and FIFO based semaphores, not priority-based semaphores or message queues.</font>
</dl>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204447"> </a><strong>Two dimensional block move</strong></font></p>
<dl>
<dt> <a name="1204448"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">A number of instructions are provided which allow two dimensional blocks or memory to be moved efficiently. This is especially useful for graphical applications.</font>
</dl>
</ul>
</blockquote>
<hr>
<table width="331" border="0" align="left" cellpadding="0" cellspacing="0">
<tr>
<td><a href="os20toc.htm"><img src="images/navtoc.gif" width="84" height="23"
border="0" alt="TOC"> </a></td>
<td><a href="c2.htm"><img src="images/navprev.gif" width="80" height="23"
border="0" alt="PREV"> </a></td>
<td><a href="c23.htm"><img src="images/navnext.gif" width="83" height="23"
border="0" alt="NEXT"> </a></td>
<td><a href="os20ix.htm"><img src="images/navidx.gif" width="84" height="23"
border="0" alt="INDEX"> </a></td>
</tr>
</table>
<font size=1 face="Verdana, Arial, Helvetica, sans-serif"> © 2001, 2002, 2003 STMicroelectronics. All Rights Reserved.<br>
ADCS 7473749B</font>
</body>
</html>
⌨️ 快捷键说明
复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?