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style="FONT-SIZE: 16pt; COLOR: red; mso-bidi-font-size: 12.0pt; mso-fareast-font-family: 黑體; mso-font-kerning: 0pt">1.<SPAN
style="FONT: 7pt 'Times New Roman'">
</SPAN></SPAN><![endif]><SPAN
style="FONT-SIZE: 16pt; COLOR: red; FONT-FAMILY: 黑體; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: 'Times New Roman'">矩陣式鍵盤接口技術(shù)及編程</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 16pt; COLOR: red; mso-bidi-font-size: 12.0pt; mso-fareast-font-family: 黑體; mso-font-kerning: 0pt"><o:p></o:p></SPAN></P>
<P
style="MARGIN-LEFT: 36pt; TEXT-INDENT: -18pt; mso-list: l1 level1 lfo4; tab-stops: list 36.0pt"><![if !supportLists]><SPAN
lang=EN-US>1.<SPAN
style="FONT: 7pt 'Times New Roman'">
</SPAN></SPAN><![endif]><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">矩陣式鍵盤的結(jié)構(gòu)與工作原理：</SPAN></P>
<P style="MARGIN-LEFT: 36pt"><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">在鍵盤中按鍵數(shù)量較多時，為了減少</SPAN><SPAN
lang=EN-US>I/O</SPAN><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">口的占用，通常將按鍵排列成矩陣形式，如圖</SPAN><SPAN
lang=EN-US>1</SPAN><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">所示。在矩陣式鍵盤中，每條水平線和垂直線在交叉處不直接連通，而是通過一個按鍵加以連接。這樣，一個端口（如</SPAN><SPAN
lang=EN-US>P1</SPAN><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">口）就可以構(gòu)成</SPAN><SPAN
lang=EN-US>4*4=16</SPAN><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">個按鍵，比之直接將端口線用于鍵盤多出了一倍，而且線數(shù)越多，區(qū)別越明顯，比如再多加一條線就可以構(gòu)成</SPAN><SPAN
lang=EN-US>20</SPAN><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">鍵的鍵盤，而直接用端口線則只能多出一鍵（</SPAN><SPAN
lang=EN-US>9</SPAN><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">鍵）。由此可見，在</SPAN></P>
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<P class=MsoNormal><SPAN lang=EN-US><IMG id=_x0000_i1025 height=333
src="鍵盤接口與編程.files/dpj281.gif" width=308></SPAN><SPAN lang=EN-US
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體"><o:p></o:p></SPAN></P></TD></TR></TBODY></TABLE>
<P style="MARGIN-LEFT: 36pt"><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">需要的鍵數(shù)比較多時，采用矩陣法來做鍵盤是合理的。</SPAN></P>
<P style="MARGIN-LEFT: 36pt"><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">矩陣式結(jié)構(gòu)的鍵盤顯然比直接法要復(fù)雜一些，識別也要復(fù)雜一些，上圖中，列線通過電阻接正電源，并將行線所接的單片機(jī)的</SPAN><SPAN
lang=EN-US>I/O</SPAN><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">口作為輸出端，而列線所接的</SPAN><SPAN
lang=EN-US>I/O</SPAN><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">口則作為輸入。這樣，當(dāng)按鍵沒有按下時，所有的輸出端都是高電平，代表無鍵按下。行線輸出是低電平，一旦有鍵按下，則輸入線就會被拉低，這樣，通過讀入輸入線的狀態(tài)就可得知是否有鍵按下了。具體的識別及編程方法如下所述。</SPAN></P>
<P
style="MARGIN-LEFT: 36pt; TEXT-INDENT: -18pt; mso-list: l1 level1 lfo4; tab-stops: list 36.0pt"><![if !supportLists]><SPAN
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