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<P><FONT face="Times New Roman Greek" size=7><STRONG>2. Interrupt &amp; 
Exception</STRONG></FONT></P>
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<P align=right><FONT face="Times New Roman TUR"><EM><STRONG>Interrupt is the 
only entrance of an OS.</STRONG></EM></FONT></P>
<P><FONT face="Courier New" 
size=2>从某种意义上来说，Interrupt是OS的唯一入口，是一个OS运行的驱动力，如果没有Interrupt，OS则是静态的；OS的各种功能，都是通过Interrupt来激活的。而Exception则是使OS具备容错能力，保证OS稳定性的一个重要因素。所以Interrupt和Exception的处理是我们在设计和开发一个OS的首要和重要部分。</FONT></P>
<P><FONT face="Courier New" 
size=2>在典型的情况下，Interrupt是为了响应一个来自于硬件的信号，而随机发生的。Interrupts被用来处理处理器外部的事件，比如敲击键盘事件。软件也可以通过执行INT 
n指令产生一个Interrupt。</FONT></P>
<P><FONT face="Courier New" 
size=2>当处理器执行一个指令的时候，如果发现一个错误条件，比如被0除，则产生一个Exception。</FONT></P>
<P><FONT face="Courier New" 
size=2>当一个Interrupt被接收，或者一个Exception被检测到的时候，CPU会暂时中止当前程序的运行，并把执行权移交给用来处理当前Interrrupt或Exception的程序模块，这个程序模块被称作Interrupt 
Service Routine(ISR)。当ISR被执行结束之后，CPU会恢复之前程序或任务的执行。这一切都被透明的执行。</FONT></P>
<P><FONT face="Courier New" 
size=2>本章的主要内容定位于Interrupt和Exception的产生机制，处理方法。</FONT></P>
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<P class=MsoNormal 
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face="Times New Roman Greek"><STRONG>Table of Contents</STRONG></FONT></P>
<P class=MsoNormal 
style="LAYOUT-GRID-CHAR: none; MARGIN: 0cm 0cm 0pt; LAYOUT-GRID-LINE: 15.6pt"><FONT 
face="Times New Roman Greek"><A 
href="interrupt-sources_1.htm" 
tppabs="http://pagoda-ooos.51.net/os_book/interrupt/interrupt-sources_1.htm">2.1 
Sources &amp; Classification</A></FONT><FONT 
face="Times New Roman Greek"></FONT></P>
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face="Times New Roman Greek"><A 
href="interrupt-vectors_2.htm" 
tppabs="http://pagoda-ooos.51.net/os_book/interrupt/interrupt-vectors_2.htm">2.2 
Vectors &amp; IDT</A></FONT></P>
<P class=MsoNormal 
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face="Times New Roman Greek"><A 
href="interrupt-priority_3.htm" 
tppabs="http://pagoda-ooos.51.net/os_book/interrupt/interrupt-priority_3.htm">2.3 
Priority &amp; Control</A></FONT></P>
<P class=MsoNormal 
style="LAYOUT-GRID-CHAR: none; MARGIN: 0cm 0cm 0pt; LAYOUT-GRID-LINE: 15.6pt"><FONT 
face="Times New Roman Greek"><A 
href="interrupt-handling_4.htm" 
tppabs="http://pagoda-ooos.51.net/os_book/interrupt/interrupt-handling_4.htm">2.4 
Handling &amp; Error Code</A></FONT></P>
<P class=MsoNormal 
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face="Times New Roman Greek"><A 
href="interrupt-8259_5.htm" 
tppabs="http://pagoda-ooos.51.net/os_book/interrupt/interrupt-8259_5.htm">2.5 
PIC-8259A</A></FONT></P>
<P class=MsoNormal 
style="LAYOUT-GRID-CHAR: none; MARGIN: 0cm 0cm 0pt; LAYOUT-GRID-LINE: 15.6pt"><FONT 
face="Times New Roman Greek"><A 
href="interrupt-sys_call_6.htm" 
tppabs="http://pagoda-ooos.51.net/os_book/interrupt/interrupt-sys_call_6.htm">2.6 
System Call</A></FONT></P></BODY></HTML>
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