lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
            <P class=MsoNormal 
            style="TEXT-INDENT: 24pt; LINE-HEIGHT: 150%; mso-char-indent-count: 2.0; mso-char-indent-size: 12.0pt" 
            align=center><SPAN lang=EN-US style="FONT-SIZE: 12pt">&nbsp;<IMG 
            height=397 src="s05-02.files/ss5-6.gif" width=500 border=0><O:P> 
            </O:P></SPAN></P>
            <P class=MsoNormal 
            style="TEXT-INDENT: 24pt; LINE-HEIGHT: 150%; TEXT-ALIGN: center; mso-char-indent-count: 2.0; mso-char-indent-size: 12.0pt" 
            align=center><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">圖</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">5</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">－</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">4<O:P> </O:P></SPAN></P>
            <P class=MsoNormal 
            style="TEXT-INDENT: 24pt; LINE-HEIGHT: 150%; TEXT-ALIGN: center; mso-char-indent-count: 2.0; mso-char-indent-size: 12.0pt" 
            align=center><SPAN lang=EN-US 
            style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></P>
            <P class=MsoNormal 
            style="TEXT-INDENT: 24pt; LINE-HEIGHT: 150%; mso-char-indent-count: 2.0; mso-char-indent-size: 12.0pt"><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">圖中</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">Dl</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">D2</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">D3</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">為三級移位寄存器，為模二加法器。移位寄存器的作用為在時鐘脈沖驅動下，能將所暫存的“</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">1</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">”或“</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">0</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">”逐級向右移。模二加法器的作用為圖中</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">(b)</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">所示的運算，即</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">0</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">十</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">0</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">＝</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">0</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">0</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">十</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">1</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">＝</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">1</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">1</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">十</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">0</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">＝</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">l</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">l</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">十</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">1</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">＝</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">0</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">。圖</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">(a)</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">D2</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">D3</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">輸出的模二和反饋為</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">Dl</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的輸入。在圖</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">(c)</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中示出，在時鐘脈沖驅動下，三級移位寄存器的暫存數據按列改變。</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">D3</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的變化即輸出序列。如移位寄存器各級的初始狀態為</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">111</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">時，輸出序列為</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">1110010</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">。在輸出周期為</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">2<SUP>3</SUP> </SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">－</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">1</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">＝</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">7</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的碼序列后，</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">D1</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">D2</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">D3</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">又回到</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">111</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">狀態。在時鐘脈沖的驅動下，輸出序列作周期性的重復。因</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">7</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">位為所能產生的最長的碼序列，</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">1110010</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">則為</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">m</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">序列。</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
            <P class=MsoNormal 
            style="TEXT-INDENT: 24pt; LINE-HEIGHT: 150%; mso-char-indent-count: 2.0; mso-char-indent-size: 12.0pt"><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">這一簡單的例子說明：</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">m</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">序列的最大長度決定于移位寄存器的級數，而碼的結構決定于反饋抽頭的位置和數量。不同的抽頭組合可以產生不同長度和不同結構的碼序列。有的抽頭組合并不能產生最長周期的序列。對于何種抽頭能產生何種長度和結構的碼序列，已經進行了大量的研究工作。現在已經得到</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">3 --- 100</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">級</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">m</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">序列發生器的連接圖和所產生的</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">m</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">序列的結構。</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
            <P class=MsoNormal 
            style="TEXT-INDENT: 24pt; LINE-HEIGHT: 150%; mso-char-indent-count: 2.0; mso-char-indent-size: 12.0pt"><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">例如</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">4</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">級移位寄存器產生的</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">15</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">位的</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">m</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">序列之一為</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">111101011001000</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">。同理我不難得到</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">31</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">63</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN