<b>手動控制</b><p>

<img src=http://www.maxim-ic.com.cn/images/appnotes/3839/3839Fig04.jpg alt="Figure 4. The MANUAL control tab lets the user define the number of bytes and intended read or write operation."><br> <i>圖4. MANUAL控制標簽允許用戶定義操作的字節數以及期望的讀或寫操作。</i><p>

用戶利用<b>MANUAL</b>控制選項(<b>圖4</b>)，來決定字節數和所需的操作。下面給出了標準單字節寫操作和雙字節讀操作的例子。<p>

<b>單字節寫操作</b>
<table border="0" cellspacing="1" cellpadding="2">
 <tr class="tablebody">
   <td><pre>START</pre></td>
   <td><pre>SEND WRITE (DEVICE<br>ADDRESS FOR WRITE)</pre></td>
   <td><pre>SEND BYTE (MEMORY<br>ADDRESS)</pre></td>
   <td><pre>SEND BYTE (DATA TO<br>BE WRITTEN)</pre></td>
   <td><pre>STOP</pre></td>
 </tr>
</table><br>
				

<b>雙字節讀操作</b>
<table border="0" cellspacing="1" cellpadding="2">
 <tr class="tablebody">
   <td><pre>START</pre></td>
   <td><pre>SEND WRITE<br>(DEVICE<br>ADDRESS<br>FOR WRITE)</pre></td>
   <td><pre>SEND BYTE<br>(MEMORY<br>ADDRESS)</pre></td>
   <td><pre>SEND<br>START<br>(REPEATED<br>START)</pre></td>
   <td><pre>SEND READ<br>(DEVICE<br>ADDRESS<br>FOR READ)</pre></td>
   <td><pre>READ WITH<br>ACK (READ<br>1ST BYTE)</pre></td>
   <td><pre>READ WITH<br>NACK (READ<br>2ND BYTE)</pre></td>
   <td><pre>STOP</td>
 </tr>
</table><br>
							

<b>重要提示：</b>當讀數據時，最后一個讀取的字節應該采用“Read with NACK”。這允許用戶根據需要讀取多個字節。需要“Read with NACK”以告知設備不要再發送更多數據。<p>

用戶可以復位I<sup>2</sup>C總線。如果用戶在手動控制的通信過程中不知怎樣操作，并且總線處于未知狀態，那么這個功能非常有用。<b>SCL</b>和<b>SDA</b> High/Low (高/低)按鈕允許用戶將這些引腳強制為期望的狀態。<p>

<h2>總結</h2>
本應用筆記結合提供的LabView VI，闡述了與DS3900通信時LabView起到的巨大作用。一旦理解了這些基本概念，用戶就可以修改VI或者復制特定模塊，以滿足特定的應用需求。<p>		<p>								 	<!-- END: DB HTML -->	<p><hr size=0><span class=text><b>我們期待您的反饋！</b><br>喜歡？不喜歡？有待改善？或為我們提供建議？<i>請與我們聯系</i> &#8212; 我們將根據您的意見或建議改善我們的工作。<a href="/feedback/forms/crm_rate.cgi?loc=www.maxim-ic.com.cn/AN3839" target="_blank">網頁評價或提供建議</a><br><br></span><hr size=0><span class=text><b>自動更新</b><br>需要自動接收最新發布的應用筆記嗎？<a href=http://www.maxim-ic.com/ee_mail/home/subscribe.mvp?phase=apn>請訂閱EE-Mail&#8482;</a> (English only)。</span><br><br><hr size=0><!-- BEGIN: MORE INFO --><a name=rp><table border=0 cellpadding=0 cellspacing=0 width="100%">	<tr valign=top>	<td><b>更多信息</b></td><td>&nbsp;</td>	<td align="right" nowrap>			APP 3839: Nov 09, 2006			</td>	</tr>	<tr valign="top">	<td colspan=3>	<table border=0 cellpadding=2 cellspacing=0 width="100%">									<tr class="tablebodyalt">	<td valign=top><a href="/quick_view2.cfm/qv_pk/4968">DS3900</a></td>	<td valign=top width='60%'>串口通信模塊，配合評估板使用</td>	<td valign=top>						<a href="/getds.cfm?qv_pk=4968">完整的數據資料</a><br>(PDF, 884kB)				</td>	<td valign=top>		</td>	</tr>			</table>	</td>	</tr><tr><td colspan=3 align="right">&nbsp;<p>	<a href="http://www.maxim-ic.com.cn/pdfserv/en/an/AN3839.pdf"><img align=absMiddle border=0 src="http://www.maxim-ic.com.cn/images/acrobat-icon.gif" ALT="下載，PDF格式" hspace=6>下載，PDF格式</a> (154kB)	<br><font color="#666666">&nbsp;AN3839,	AN 3839,	APP3839,	Appnote3839,	Appnote 3839</font></td></tr></table><!-- END: MORE INFO --></td></tr></table>		</td></tr>	<tr>	<td colspan="2"><img src="http://www.maxim-ic.com.cn/images/clear.gif" width="1" height="10"></td>	</tr>	</table></td><td><img src="http://www.maxim-ic.com.cn/images/clear.gif" width="8" height="1"></td></tr></table>	<!-- ================================================================== --><!-- BEGIN: SITE FOOTER --><!-- ================================================================== --><!-- BEGIN: FOOTER JAVASCRIPT --><script language="JavaScript1.1"><!-- // [ HIDE JAVASCRIPT ]function open_crm_win(mode, w, h){    var window_name = 'maxim_crm_' + mode + '_win'; 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