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<div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"><strong>(</strong><strong>1</strong><strong>)</strong><strong> RS-232</strong><strong>的历史和作用</strong></div>
<div style="MARGIN: 0cm="0cm" 2.85pt 0pt="0pt" 6pt; TEXT-INDENT: 21pt; LINE-HEIGHT: normal" align="left">在串行通讯时，要求通讯双方都采用一个标准接口，使不同 的设备可以方便地连接起来进行 通讯。 RS-232-C接口（又称 EIA RS-232-C）是目前最常用的一种串行通讯接口。</div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">（“RS-232-C”中的”-C”只不过表示RS-232的版本，所以与RS-232简称是一样的）它 是在 1970年由美国电子工业协会（EIA）联合贝尔系统、调制解调器厂家及计算机终端生产 厂家共同制定的用于串行通讯的标 准。它的全名是"数据终端设备（DTE）和数据通讯设备（DCE）之间 串行二进制数据交换接口技术标准"该标准规定采用一个 25个脚的 DB-25连接 器，对连接器的每个引脚的信号内容加以规定，还对各种信 号的电平加以规定。后来 IBM的 PC机将 RS-232简化成了DB-9连接器，从而成为事实标准。而工业控制的RS-232口一般 只使用 RXD、TXD、GND三条线。</div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"> <img alt="" src="https://www.elecfans.com/article/UploadPic/2008-10/2008102102742251.jpg"/></div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"><strong>(2)RS-232</strong><strong>接口的电气特性</strong></div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; TEXT-INDENT: 21pt; LINE-HEIGHT: normal" align="left">在 RS-232-C中任何一条信号线的电压均为负逻辑关系。即：逻 辑"1"为-3到-15V；逻辑"0"</div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">为 +3到+15V 。</div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">RS-232-C最常用的 9条引线的信号内容如下所示</div> <table style="BORDER-RIGHT: medium="medium" none; BORDER-TOP: medium="medium" none; MARGIN-LEFT: 6pt; BORDER-LEFT: medium="medium" none; BORDER-BOTTOM: medium="medium" none; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" border="1"> <tbody> <tr style="HEIGHT: 13.1pt"> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: windowtext="windowtext" 1pt="1pt" solid; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext="windowtext" 1pt="1pt" solid; WIDTH: 34.45pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="46"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">DB-9</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: windowtext="windowtext" 1pt="1pt" solid; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 177.9pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="237"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal; TEXT-ALIGN: left" align="left">1 2 3 4 5 6 7 8</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: windowtext="windowtext" 1pt="1pt" solid; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 15.9pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="21"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">9</div></td></tr> <tr style="HEIGHT: 15.6pt"> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext="windowtext" 1pt="1pt" solid; WIDTH: 34.45pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="46"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">DB-25</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 177.9pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="237"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal; TEXT-ALIGN: left" align="left">8 3 2 20 7 6 4 5</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 15.9pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="21"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">22</div></td></tr> <tr style="HEIGHT: 13.1pt"> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext="windowtext" 1pt="1pt" solid; WIDTH: 34.45pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="46"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">定义</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 177.9pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="237"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">DCD RXD TXD DTR GND DSR RTS CTS</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 15.9pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="21"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">RI</div></td></tr></tbody></table> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"><strong></strong> </div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"><strong>(3)</strong><strong> RS-232</strong><strong>接口的物理结构</strong></div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; TEXT-INDENT: 18.85pt; LINE-HEIGHT: normal" align="left">RS-232-C接口连接器一般使用型号为 DB-9插头座,通常插头在 DCE端,插座在 DTE端.</div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">PC机的 RS-232口为 9芯针插座。而波士 RS-232/RS-485转换器的 RS-232为 DB-9孔插头。 一些设备与 PC机连接的 RS-232接口,因为不使用对方的传送控制信号,只需三条接口线, 即"发送数据 TXD"、"接收数据 RXD"和"信号地 GND"。RS-232传输线采用屏蔽双绞线。</div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"><strong></strong> </div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"><strong>（</strong><strong>4</strong><strong>）</strong><strong>RS-232</strong><strong>传输电缆长度</strong></div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; TEXT-INDENT: 21pt; LINE-HEIGHT: normal" align="left">由 RS-232C标准规定在码元畸变小于4%的情况下，传输电缆长度应为50英尺，其实这个4% 的码元畸变是很保守的，在实际应用中，约有 99%的用户是按码元畸变 10-20%的范围工作的， 所以实际使用中最大距离会远超过 50英尺，美国 DEC公司曾规定允许码元畸变为 10%而得出 下面实验结果。其中 1 号电缆为屏蔽电缆，型号为 DECP.NO.9107723内有三对双绞线，每对</div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">由 22#AWG组成，其外覆以屏蔽网。2号电缆为不带屏蔽的电缆。型号为 DECP.NO.9105856-04</div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">是 22#AWG的四芯电缆。</div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"><strong></strong> </div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"><strong><u>DEC</u></strong><strong><u> </u></strong><strong><u>公司的实验结果</u></strong></div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; TEXT-INDENT: 31.5pt; LINE-HEIGHT: normal; TEXT-ALIGN: left" align="left">波特率 bps 1 号电缆传输距离（米） 2 号电缆传输距离（米）</div> <table style="BORDER-RIGHT: medium="medium" none; BORDER-TOP: medium="medium" none; MARGIN-LEFT: 27.15pt; BORDER-LEFT: medium="medium" none; BORDER-BOTTOM: medium="medium" none; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" border="1"> <tbody> <tr style="HEIGHT: 13.1pt"> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: windowtext="windowtext" 1pt="1pt" solid; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext="windowtext" 1pt="1pt" solid; WIDTH: 81.8pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="109"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">110</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: windowtext="windowtext" 1pt="1pt" solid; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 161.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="215"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">1500</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: windowtext="windowtext" 1pt="1pt" solid; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 95.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="127"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">900</div></td></tr> <tr style="HEIGHT: 15.6pt"> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext="windowtext" 1pt="1pt" solid; WIDTH: 81.8pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="109"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">300</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 161.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="215"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">1500</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 95.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="127"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">900</div></td></tr> <tr style="HEIGHT: 15.6pt"> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext="windowtext" 1pt="1pt" solid; WIDTH: 81.8pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="109"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">1200</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 161.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="215"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">900</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 95.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="127"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">900</div></td></tr> <tr style="HEIGHT: 15.6pt"> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext="windowtext" 1pt="1pt" solid; WIDTH: 81.8pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="109"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">2400</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 161.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="215"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">300</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 95.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="127"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">150</div></td></tr> <tr style="HEIGHT: 15.6pt"> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext="windowtext" 1pt="1pt" solid; WIDTH: 81.8pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="109"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">4800</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 161.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="215"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">300</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 95.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 15.6pt" valign="top" width="127"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">75</div></td></tr> <tr style="HEIGHT: 13.1pt"> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext="windowtext" 1pt="1pt" solid; WIDTH: 81.8pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="109"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">9600</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 161.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="215"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">75</div></td> <td style="BORDER-RIGHT: windowtext="windowtext" 1pt="1pt" solid; PADDING-RIGHT: 0cm; BORDER-TOP: medium="medium" none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium="medium" none; WIDTH: 95.05pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext="windowtext" 1pt="1pt" solid; HEIGHT: 13.1pt" valign="top" width="127"> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">75</div></td></tr></tbody></table> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"> </div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; TEXT-INDENT: 21pt; LINE-HEIGHT: normal" align="left">经过许多年来RS-232器件以及通信技术的改进，RS-232的通信距离已经大大增加。波士</div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left">电子的 RS-232增强器可以将普通的 RS-232口的通信距离直接延长到 1000米。<br/></div> <div style="MARGIN: 0cm="0cm" 2.85pt 0pt; LINE-HEIGHT: normal" align="left"><b><a href="https://www.elecfans.com/soft/78/223/2008/200804263313.html">max232芯片中文资料</a></b></div> 
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