📄 ——单片机系统在测控领域的稳定性探讨.htm
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lang=EN-US><o:p></o:p></SPAN></B></P>
<P class=MsoNormal style="TEXT-INDENT: 21.75pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">当乱飞的程序进入非程序区的时候，</SPAN>
<SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">我们就可设定软件陷阱对乱飞的程序进行拦截从而将程序引向一个固定的位置。这样我们就可将捕获的程序重新纳入正轨。</SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21.75pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">软件陷阱主要就是把程序从新引入它的复位入口处，也就是说我们在适当的地方设置这样的指令：</SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21.75pt"><SPAN
lang=EN-US>NOP</SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21.75pt"><SPAN lang=EN-US>NOP
</SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21.75pt"><SPAN
lang=EN-US>LJMP<SPAN style="mso-spacerun: yes">
</SPAN>0000H</SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21.75pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">对于软件陷阱的安排，我们主要安排在这样一些区域，未使用的中断区，未使用的</SPAN><SPAN
lang=EN-US>EPROM</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">空间及非</SPAN><SPAN
lang=EN-US>EPROM</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">空间。程序运行区，及中断服务程序区。在这里我们主要来看前三种：</SPAN></P>
<P class=MsoNormal
style="MARGIN-LEFT: 39.75pt; TEXT-INDENT: -18pt; mso-list: l1 level1 lfo2; tab-stops: list 39.75pt"><SPAN
lang=EN-US>1、<SPAN style="FONT: 7pt 'Times New Roman'">
</SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">未使用的中断区</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21.75pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">如果对于未使用的中断因干扰而开放的话，我们可以把中断服务程序这样来写：</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21.75pt"><SPAN lang=EN-US>NOP
</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21.75pt"><SPAN
lang=EN-US>NOP</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21.75pt"><SPAN
lang=EN-US>POP<SPAN style="mso-spacerun: yes">
</SPAN>D1<SPAN style="mso-spacerun: yes">
</SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">；将原来的错误断点弹出</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21.75pt"><SPAN
lang=EN-US>POP<SPAN style="mso-spacerun: yes">
</SPAN>D2<SPAN style="mso-spacerun: yes">
</SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">；将原来的错误断点弹出</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21.75pt"><SPAN
lang=EN-US>PUSH<SPAN style="mso-spacerun: yes">
</SPAN>00H</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21.75pt"><SPAN
lang=EN-US>PUSH<SPAN style="mso-spacerun: yes">
</SPAN>00H<SPAN style="mso-spacerun: yes">
</SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">；将断点地址重写为</SPAN><SPAN
lang=EN-US>0000H</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21.75pt"><SPAN
lang=EN-US>RETI</SPAN></P>
<P class=MsoNormal
style="MARGIN-LEFT: 39.75pt; TEXT-INDENT: -18pt; mso-list: l1 level1 lfo2; tab-stops: list 39.75pt"><SPAN
lang=EN-US>2、<SPAN style="FONT: 7pt 'Times New Roman'">
</SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">未使用的</SPAN><SPAN
lang=EN-US>EPROM</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">区</SPAN></P>
<P class=MsoNormal
style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">假设我们用了一片</SPAN><SPAN
lang=EN-US>2764</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，但并没有用完整个存储区。这时候就可在未用的区域里填充上</SPAN><SPAN
lang=EN-US>020000</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">数据，这样当程序飞入其中时就会很快的走入正轨。这条指令其实是“</SPAN><SPAN
lang=EN-US>LJMP<SPAN style="mso-spacerun: yes">
</SPAN>0000H</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">”的机器码。</SPAN></P>
<P class=MsoNormal
style="MARGIN-LEFT: 39.75pt; TEXT-INDENT: -18pt; mso-list: l1 level1 lfo2; tab-stops: list 39.75pt"><SPAN
lang=EN-US>3、<SPAN style="FONT: 7pt 'Times New Roman'">
</SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">非</SPAN><SPAN
lang=EN-US>EPROM</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">空间</SPAN></P>
<P class=MsoNormal
style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">单片机系统的程序空间是</SPAN><SPAN
lang=EN-US>64K</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，正常情况下我们所使用的</SPAN><SPAN
lang=EN-US>EPROM</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">不会占用所有的空间，假设我们现在的</SPAN><SPAN
lang=EN-US>EPROM</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">占用</SPAN><SPAN
lang=EN-US>16K</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的空间那么剩下的</SPAN><SPAN
lang=EN-US>48K</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">空间就被闲置不用了。当乱飞的</SPAN><SPAN
lang=EN-US>PC</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">落入这些空间时，读入的数据将为</SPAN><SPAN
lang=EN-US>FFH</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，这是</SPAN>
<SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">：</SPAN><SPAN
lang=EN-US>MOV<SPAN style="mso-spacerun: yes">
</SPAN>R7</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，</SPAN><SPAN
lang=EN-US>A<SPAN style="mso-spacerun: yes">
</SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">指令的机器码，将修改</SPAN><SPAN
lang=EN-US>R7</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的内容。因此，当程序乱飞入非</SPAN><SPAN
lang=EN-US>EPROM</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">芯片区后，不仅无法导入正规，面且破坏了</SPAN><SPAN
lang=EN-US>R7</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的内容。</SPAN></P>
<P class=MsoNormal
style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">我们知道，当</SPAN><SPAN
lang=EN-US>CPU</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">读程序存储器的时候，伴随着会产生一个</SPAN><SPAN
lang=EN-US>PSEN</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">信号，我们就可利用这个信号，再加上一个非</SPAN><SPAN
lang=EN-US>EPROM</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">区的地址译码信号，构成一个选通信号来起动一个空闲的中断，再用软件陷井的方法从中断程序中把程序导入正规。我们可看下面的一个图：</SPAN></P>
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