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style="FONT: 7pt 'Times New Roman'">
</SPAN></SPAN><![endif]><SPAN
style="FONT-SIZE: 16pt; COLOR: red; FONT-FAMILY: 黑体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: 'Times New Roman'">矩阵式键盘接口技术及编程</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 16pt; COLOR: red; mso-bidi-font-size: 12.0pt; mso-fareast-font-family: 黑体; mso-font-kerning: 0pt"><o:p></o:p></SPAN></P>
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lang=EN-US>1.<SPAN
style="FONT: 7pt 'Times New Roman'">
</SPAN></SPAN><![endif]><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">矩阵式键盘的结构与工作原理：</SPAN></P>
<P style="MARGIN-LEFT: 36pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">在键盘中按键数量较多时，为了减少</SPAN><SPAN
lang=EN-US>I/O</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">口的占用，通常将按键排列成矩阵形式，如图</SPAN><SPAN
lang=EN-US>1</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">所示。在矩阵式键盘中，每条水平线和垂直线在交叉处不直接连通，而是通过一个按键加以连接。这样，一个端口（如</SPAN><SPAN
lang=EN-US>P1</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">口）就可以构成</SPAN><SPAN
lang=EN-US>4*4=16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个按键，比之直接将端口线用于键盘多出了一倍，而且线数越多，区别越明显，比如再多加一条线就可以构成</SPAN><SPAN
lang=EN-US>20</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">键的键盘，而直接用端口线则只能多出一键（</SPAN><SPAN
lang=EN-US>9</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">键）。由此可见，在</SPAN></P>
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<P class=MsoNormal><SPAN lang=EN-US><IMG id=_x0000_i1025 height=333
src="键盘接口与编程.files/dpj281.gif" width=308></SPAN><SPAN lang=EN-US
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"><o:p></o:p></SPAN></P></TD></TR></TBODY></TABLE>
<P style="MARGIN-LEFT: 36pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">需要的键数比较多时，采用矩阵法来做键盘是合理的。</SPAN></P>
<P style="MARGIN-LEFT: 36pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">矩阵式结构的键盘显然比直接法要复杂一些，识别也要复杂一些，上图中，列线通过电阻接正电源，并将行线所接的单片机的</SPAN><SPAN
lang=EN-US>I/O</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">口作为输出端，而列线所接的</SPAN><SPAN
lang=EN-US>I/O</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">口则作为输入。这样，当按键没有按下时，所有的输出端都是高电平，代表无键按下。行线输出是低电平，一旦有键按下，则输入线就会被拉低，这样，通过读入输入线的状态就可得知是否有键按下了。具体的识别及编程方法如下所述。</SPAN></P>
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