141 lines
8.3 KiB
HTML
141 lines
8.3 KiB
HTML
<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns:MadCap="http://www.madcapsoftware.com/Schemas/MadCap.xsd" MadCap:lastBlockDepth="6" MadCap:lastHeight="94" MadCap:lastWidth="853" MadCap:disableMasterStylesheet="true" MadCap:tocPath="" MadCap:InPreviewMode="false" MadCap:PreloadImages="false" MadCap:RuntimeFileType="Topic" MadCap:TargetType="WebHelp" lang="en-us" xml:lang="en-us" MadCap:PathToHelpSystem="../../../" MadCap:HelpSystemFileName="Default.xml" MadCap:SearchType="Stem">
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<head><title>COUNT</title>
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<link href="../../SkinSupport/MadCap.css" rel="stylesheet" />
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<link href="../../Resources/Stylesheets/BSE_Help.css" rel="stylesheet" />
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<script src="../../SkinSupport/MadCapAll.js" type="text/javascript">
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</script>
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</head>
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<body>
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<h1 class="code">COUNT</h1>
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<div class="ImagePlusCaption">
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<div class="Col2">
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<p>
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<img src="../../graphics/pgm_icon2.gif" border="0" alt="BS2 icon" title="BS2 icon" />
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<img src="../../graphics/pgm_icon2e.gif" border="0" alt="BS2e icon" title="BS2e icon" />
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<img src="../../graphics/pgm_icon2sx.gif" border="0" alt="BS2sx icon" title="BS2sx icon" />
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<img src="../../graphics/pgm_icon2p.gif" border="0" alt="BS2p icon" title="BS2p icon" />
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<img src="../../graphics/pgm_icon2pe.gif" border="0" alt="BS2pe icon" title="BS2pe icon" />
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<img src="../../graphics/pgm_icon2px.gif" border="0" alt="BS2px icon" title="BS2px icon" />
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</p>
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</div>
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<p style="text-align: right;"><a href="../ExampleTopics/CountEx.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">COUNT Example</a>
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</p>
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<p> </p>
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</div>
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<p class="clear"> </p>
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<p> </p>
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<p>Syntax: <span class="keyword_in_text">COUNT</span> <![CDATA[ ]]><i>Pin</i>,<i> Duration</i>,<i> Variable</i></p>
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<h2>Function</h2>
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<p class="PlainText">Count the number of cycles (0-1-0 or 1-0-1) on the specified pin during the <i>Duration</i> time frame and store that number in <i>Variable</i>.
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</p>
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<ul>
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<li value="1"><b><i>Pin</i></b> is a variable/constant/expression (0 – 15) that specifies
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the I/O pin to use. This pin will be set to input mode.</li>
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<li value="2"><b><i>Duration</i></b> is a variable/constant/expression (1 – 65535) specifying
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the time during which to count. The unit of time for <i>Duration</i> is described
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below.</li>
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<li value="3"><b><i>Variable</i></b> is a variable (usually a Word) in which the count will
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be stored.</li>
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</ul>
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<h2>Quick Facts<br /></h2>
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<table width="100%" cellpadding="4" cellspacing="0" border="1">
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<tr>
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<td width="20%" align="center" bgcolor="#CFCFCF"> </td>
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<td width="16%" align="center" bgcolor="#CFCFCF">BS2 / BS2e</td>
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<td width="16%" align="center" bgcolor="#CFCFCF">BS2sx</td>
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<td width="16%" align="center" bgcolor="#CFCFCF">BS2p</td>
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<td width="16%" align="center" bgcolor="#CFCFCF">BS2pe</td>
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<td width="16%" align="center" bgcolor="#CFCFCF">BS2px</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Units in <i>Duration</i></td>
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<td align="center">1 ms</td>
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<td align="center">400 µs</td>
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<td align="center">287 µs</td>
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<td align="center">720 µs</td>
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<td align="center">287 µs</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF"><i>Duration</i> range</td>
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<td align="center">1 ms to 65.535 s</td>
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<td align="center">400 µs to 26.214 s</td>
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<td align="center">287 µs to 18.809 s</td>
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<td align="center">720 µs to 47.180 s</td>
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<td align="center">287 µs to 18.809 s</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Minimum pulse width</td>
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<td align="center">4.16 µs</td>
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<td align="center">1.66 µs</td>
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<td align="center">1.20 µs</td>
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<td align="center">3.00 µs</td>
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<td align="center">1.20 µs</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Maximum frequency<br></br>(square wave)</td>
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<td align="center">120,000 Hz</td>
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<td align="center">300,000 Hz</td>
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<td align="center">416,700 Hz</td>
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<td align="center">166,667 Hz</td>
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<td align="center">416,700 Hz</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Related Commands</td>
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<td align="center" colspan="5">
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<p colspan="5" align="center"><a href="PULSIN.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">PULSIN</a>
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</p>
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</td>
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</tr>
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</table>
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<h2>Explanation</h2>
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<p class="PlainText">The <span class="keyword_in_text">COUNT</span> instruction makes the <i>Pin</i> an input, then for the specified
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<i>duration</i>, counts cycles on that pin and stores the total in a variable. A
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cycle is a change in state from 1 to 0 to 1, or from 0 to 1 to 0.</p>
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<p class="PlainText">According to table above, <span class="keyword_in_text">COUNT</span> on the BS2 can respond to transitions
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(pulse widths) as small as 4.16 microseconds (µs). A cycle consists of two transitions
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(e.g., 0 to 1, then 1 to 0), so <span class="keyword_in_text">COUNT</span> (on the BS2) can respond to square
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waves with periods as short as 8.32 µs; up to 120 kilohertz (kHz) in frequency.
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For non-square waves (those whose high time and low time are unequal), the shorter
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of the high and low times must be at least 4.16 µs in width (on the BS2). Refer
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to the table for data on other BASIC Stamp modules.</p>
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<p class="PlainText">If you use <span class="keyword_in_text">COUNT</span> on slowly changing analog waveforms like sine waves,
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you may find that the value returned is higher than expected. This is because the
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waveform may pass through the BASIC Stamp’s 1.4-volt logic threshold slowly enough
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that noise causes false counts. You can fix this by passing the signal through
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a Schmitt Trigger, like one of the inverters of a 74HCT14. Or, you may use the
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BS2px’s built-in Schmitt-Trigger pin property; see
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<a href="CONFIGPIN.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">CONFIGPIN</a> for details. </p>
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<div class="Col2">
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<div class="MasterFoot">
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<p MadCap:conditions="BSEconditions.BSEWebHelp (Primary)-INCLUDE"><a href="../../HomeTopics/HomePage.htm">Go to Welcome page</a>
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</p>
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</div>
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</div>
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<div class="Col2">
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<div class="MasterFoot">
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<p style="text-align: right;"><span class="ContactInfoProjectName">BASIC Stamp Help</span> <![CDATA[ ]]><span class="ContactInfoVersion#">Version 2.5.4</span> <![CDATA[ ]]></p>
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<p style="text-align: right;">Copyright © <span class="ContactInfoCompanyName">Parallax Inc.</span></p>
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<p style="text-align: right;"><span class="SystemShortDate">8/8/2012</span>
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</p>
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</div>
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</div>
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