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<body> <script type="text/javascript" language="javascript" src="/js/random_bbild.js"></script> <script type="text/javascript" LANGUAGE="JavaScript">  </script> <p>   <table border="0" width="534" cellspacing="0" cellpadding="0"> <tr valign="TOP"> <td width="25"></td> <td width="505" colspan="3"> <h1>The CAN Protocol Tour </h1> </td> </tr> <tr align="LEFT" valign="TOP"> <td width="25"></td> <td width="505" colspan="3"> <h3><b>Introduction</b></h3> <hr size="1" color="#3366cc"> </td> </tr> <tr align="LEFT" valign="TOP"> <td height="20" width="25"></td> <td width="505" colspan="3"> <p>This is a brief introduction to the CAN protocol. We do not claim completeness; if you want to know everything you should <a target="_top" href="/download">obtain the Bosch specification</a> from our Download Area.  </p> <p>A note about the specifications: the spec that Bosch wrote is very clear and readable, but it's not the ISO11898 spec. That spec isn't available on the net; instead you have to buy it from ISO. </p> <h4> Overview of the CAN Protocol Tour</h4> <ul> <li><a href="main.htm">Introduction  </a></li> <li><font color="#0000FF"><a href="canprot1.htm">CAN Messages 1/3</a></font></li> <li><font color="#0000FF"><a href="canprot2.htm"> CAN Messages 2/3</a></font></li> <li><font color="#0000FF"><a href="canprot3.htm">CAN Messages 3/3</a></font></li> <li><font color="#0000FF"><a href="canphys.htm">CAN Physical Layers </a></font></li> <li><font color="#0000FF"><a href="can_scope_pictures.htm">CAN oscilloscope pictures </a></font></li> <li><font color="#0000FF"><a href="conn.htm">CAN Connectors</a></font></li> <li><font color="#0000FF"><a href="canbit.htm">CAN Bit Timing </a></font></li> <li><font color="#0000FF"><a href="canerror.htm">CAN Error Handling </a></font></li> </ul> <h4><b>The CAN bus</b></h4> <p>The CAN bus is a broadcast type of bus. This means that all nodes can "hear" all transmissions. There is no way to send a message to just a specific node; all nodes will invariably pick up all traffic. The CAN hardware, however, provides local filtering so that each node may react only on the interesting messages.</p> <p>The bus uses Non-Return To Zero (NRZ) with bit-stuffing. The modules are connected to the bus in a wired-and fashion: if just one node is driving the bus to a logical 0, then the whole bus is in that state regardless of the number of nodes transmitting a logical 1.</p> <p>The CAN standard defines four different message types. The messages uses a clever scheme of <a href="canprot1.htm">bit-wise arbitration</a> to control access to the bus, and each message is tagged with a <a href="canprot1.htm">priority</a>.</p> <p>The CAN standard also defines an elaborate scheme for error handling and confinement which is described in more detail <a href="canerror.htm">here</a>.</p> <p>Bit timing and clock synchronization is discussed <a href="canbit.htm">here</a>. Here's <a href="timing_calc.htm">a bit timing calculator</a> you can use to calculate the CAN bus parameters and register settings. </p> <p>CAN may implemented using <a href="canphys.htm">different physical layers, some of which are described here</a>, and there are also a fair number of <a href="conn.htm">connector types</a> in use. Here's a<a href="can_scope_pictures.htm"> number of oscilloscope pictures</a> for those interested in the details of a message.</p> <hr size="1" color="#3366cc"> </td> </tr> <tr align="LEFT" valign="TOP"> <td height="10" width="25"></td> <td height="10" width="166"> <h3></h3> </td> <td height="10" width="61"> </td> <td height="10" width="274"> <a href="canprot1.htm"><b> CAN Messages, page 1 of 3 - 2/9 >></b></a> </td> </tr> <tr align="LEFT" valign="TOP"> <td height="10" width="25"></td> <td height="10" width="505" colspan="3"> <hr size="1" color="#3366cc"> <p>  </td> </tr> <tr align="LEFT" valign="TOP"> <td height="44" colspan="4" width="532">  </td> </tr> </table> <hr size=1 color="#3366cc"> <img border="0" src="/global/images/gfx/blank.gif" width="18" height="5">© Kvaser AB - All rights reserved | <a href="/corporate/address.htm" target="_self">Contact us</a> | <a href="/corporate/address.htm#webmaster" target="_self">Webmaster </a>| <a href="/sitemap.htm" target="_self">Sitemap</a><br> <img border="0" src="/global/images/gfx/blank.gif" width="18" height="5"><font size="1"><i>Direct link to this page: <script type="text/javascript" language="javascript" src="/js/url.js"></script></font></i><p> <script type="text/javascript" language="javascript1.2" src="/js/menu.js"></script> <script src="http://www.google-analytics.com/urchin.js" type="text/javascript"> </script> <script type="text/javascript"> _uacct = "UA-3048325-1"; urchinTracker(); </script>  <p></body>