1*9c2daa00SOllivier Robert<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2*9c2daa00SOllivier Robert<html> 3*9c2daa00SOllivier Robert<head> 4*9c2daa00SOllivier Robert<meta http-equiv="content-type" content="text/html;charset=iso-8859-1"> 5*9c2daa00SOllivier Robert<meta name="generator" content="HTML Tidy, see www.w3.org"> 6*9c2daa00SOllivier Robert<title>Reference Clock Support</title> 7*9c2daa00SOllivier Robert<link href="scripts/style.css" type="text/css" rel="stylesheet"> 8*9c2daa00SOllivier Robert</head> 9*9c2daa00SOllivier Robert<body> 10*9c2daa00SOllivier Robert<h3>Reference Clock Support</h3> 11*9c2daa00SOllivier Robert<img src="pic/stack1a.jpg" alt="gif" align="left">Master Time Facility at the <a href="http://www.eecis.udel.edu/%7emills/lab.html">UDel Internet Research Laboratory</a> 12*9c2daa00SOllivier Robert<p>Last update: 13*9c2daa00SOllivier Robert <!-- #BeginDate format:En2m -->10-Mar-2014 05:20<!-- #EndDate --> 14*9c2daa00SOllivier Robert UTC</p> 15*9c2daa00SOllivier Robert<br clear="left"> 16*9c2daa00SOllivier Robert<h4>Related Links</h4> 17*9c2daa00SOllivier Robert<script type="text/javascript" language="javascript" src="scripts/hand.txt"></script> 18*9c2daa00SOllivier Robert<script type="text/javascript" language="javascript" src="scripts/refclock.txt"></script> 19*9c2daa00SOllivier Robert<script type="text/javascript" language="javascript" src="scripts/audio.txt"></script> 20*9c2daa00SOllivier Robert<h4>Table of Contents</h4> 21*9c2daa00SOllivier Robert<ul> 22*9c2daa00SOllivier Robert <li class="inline"><a href="#intro">Introduction</a></li> 23*9c2daa00SOllivier Robert <li class="inline"><a href="#spec">Special Considerations</a></li> 24*9c2daa00SOllivier Robert <li class="inline"><a href="#list">List of Reference Clock Drivers</a></li> 25*9c2daa00SOllivier Robert</ul> 26*9c2daa00SOllivier Robert<hr> 27*9c2daa00SOllivier Robert<h4 id="intro">Introduction</h4> 28*9c2daa00SOllivier Robert<p>NTP Version 4 supports almost four dozen satellite, radio and telephone modem reference clocks plus several audio devices for instrumentation signals. A general description of the reference clock support is on this page. Additional information about each reference clock driver can be found via links from this page. Additional information is on the <a href="rdebug.html">Debugging Hints for Reference Clock Drivers</a> and <a href="howto.html">How To Write a Reference Clock Driver</a> pages. Information on how to support pulse-per-second (PPS) signals produced by some devices is on the <a href="pps.html">Pulse-per-second (PPS) Signal Interfacing</a> page. All reference clock drivers require that the reference clock use only Coordinated Universal Time (UTC). Timezone and standard/daylight adjustments are performed by the operating system kernel.</p> 29*9c2daa00SOllivier Robert<p>A reference clock will generally (though not always) be a radio timecode receiver synchronized to standard time as provided by NIST and USNO in the US, NRC in Canada and their counterparts elsewhere in the world. A device driver specific to each reference clock must be compiled in the distribution; however, most common radio, satellite and telephone modem clocks are included by default and are activated by configuration commands.</p> 30*9c2daa00SOllivier Robert<p>Reference clocks are supported in the same way as ordinary NTP clients and use the same filter, select, cluster and combine algorithms. Drivers have addresses in the form 127.127.<i>t.u</i>, where <i>t</i> is the driver type and <i>u</i> is a unit number in the range 0-3 to distinguish multiple instances of the same driver. The connection to the computer is device dependent, usually a serial port, parallel port or special bus peripheral, but some can work directly from an audio codec or sound card. The particular device is specified by adding a soft link from the name used by the driver to the particular device name.</p> 31*9c2daa00SOllivier Robert<p>The <tt>server</tt> command is used to configure a reference clock. Only the <tt>mode</tt>, <tt>minpoll</tt>, <tt>maxpoll</tt>, and <tt>prefer</tt> options are supported for reference clocks, as described on the <a href="clockopt.html">Reference Clock Commands</a> page. The <tt>prefer</tt> option is discussed on the <a href="prefer.html">Mitigation Rules and the <tt>prefer</tt> Keyword</a> page. Some of these options have meaning only for selected clock drivers.</p> 32*9c2daa00SOllivier Robert<p>The <tt>fudge</tt> command can be used to provide additional information for individual drivers and normally follows immediately after the <tt>server</tt> command. The reference clock stratum is by default 0, so that the server stratum appears to clients as 1. The <tt>stratum</tt> option can be used to set the stratum to any value in the range 0 through 15. The <tt>refid</tt> option can be used to change the reference identifier, as might in the case when the driver is disciplined by a pulse-per-second (PPS) source. The device-dependent <tt>mode</tt>, <tt>time</tt> and <tt>flag</tt> options can provide additional driver customization.</p> 33*9c2daa00SOllivier Robert<h4 id="spec">Special Considerations</h4> 34*9c2daa00SOllivier Robert<p>The <a href="audio.html">Audio Drivers</a> page describes three software drivers that process audio signals from an audio codec or sound card. One is for the NIST time and frequency stations WWV and WWVH, another for the Canadian time and frequency station CHU. These require an external shortwave radio and antenna. A third is for the generic IRIG signal produced by some timing devices. Currently, these are supported in FreeBSD, Solaris and SunOS and likely in other system as well.</p> 35*9c2daa00SOllivier Robert<p>The <a href="drivers/driver1.html"> Undisciplined Local Clock</a> driver can simulate a reference clock when no external synchronization sources are available. If a server with this driver is connected directly or indirectly to the public Internet, there is some danger that it can destabilize other clients. It is not recommended that the local clock driver be used in this way, as the orphan mode described on the <a href="assoc.html">Association Management</a> page provides a generic backup capability.</p> 36*9c2daa00SOllivier Robert<p>The local clock driver can also be used when an external synchronization source such as the IEEE 1588 Precision Time Protocol or NIST Lockclock directly synchronizes the computer time. Further information is on the <a href="extern.html">External Clock Discipline and the Local Clock Driver</a> page.</p> 37*9c2daa00SOllivier Robert<p>Several drivers make use of the pulse-per-second (PPS) signal discipline, which is part of the generic driver interface, so require no specific configuration. For those drivers that do not use this interface, the <a href="drivers/driver22.html"> PPS Clock Discipline</a> driver can be can provide this function. It normally works in conjunction with the reference clock that produces the timecode signal, but can work with another driver or remote server. When PPS kernel features are present, the driver can redirect the PPS signal to the kernel.</p> 38*9c2daa00SOllivier Robert<p>Some drivers depending on longwave or shortwave radio services need to know the radio propagation time from the transmitter to the receiver. This must be calculated for each specific receiver location and requires the geographic coordinates of both the transmitter and receiver. The transmitter coordinates for various radio services are given in the <a href="http://www.eecis.udel.edu/%7emills/ntp/qth.html">Time and Frequency Standard Station Information</a> page. Receiver coordinates can be obtained locally or from Google Earth. The actual calculations are beyond the scope of this document.</p> 39*9c2daa00SOllivier Robert<p>Depending on interface type, port speed, etc., a reference clock can have a small residual offset relative to another. To reduce the effects of jitter when switching from one driver to the another, it is useful to calibrate the drivers to a common ensemble offset. The <tt>enable calibrate</tt> configuration command described on the <a href="miscopt.html">Miscellaneous Options</a> page activates a special feature which automatically calculates a correction factor for each driver relative to an association designated the prefer peer.</p> 40*9c2daa00SOllivier Robert<h4 id="list"> List of Reference Clock Drivers</h4> 41*9c2daa00SOllivier Robert<p>Following is a list showing the type and title of each driver currently implemented. The compile-time identifier for each is shown in parentheses. Click on a selected type for specific description and configuration documentation, including the clock address, reference ID, driver ID, device name and serial line speed. For those drivers without specific documentation, please contact the author listed in the <a href="copyright.html">Copyright Notice</a> page.</p> 42*9c2daa00SOllivier Robert<ul> 43*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver1.html">Type 1</a> Undisciplined Local Clock (<tt>LOCAL</tt>)</li> 44*9c2daa00SOllivier Robert <li class="inline">Type 2 Deprecated: was Trak 8820 GPS Receiver</li> 45*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver3.html">Type 3</a> PSTI/Traconex 1020 WWV/WWVH Receiver (<tt>WWV_PST</tt>)</li> 46*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver4.html">Type 4</a> Spectracom WWVB/GPS Receivers (<tt>WWVB_SPEC</tt>)</li> 47*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver5.html">Type 5</a> TrueTime GPS/GOES/OMEGA Receivers (<tt>TRUETIME</tt>)</li> 48*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver6.html">Type 6</a> IRIG Audio Decoder (<tt>IRIG_AUDIO</tt>)</li> 49*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver7.html">Type 7</a> Radio CHU Audio Demodulator/Decoder (<tt>CHU</tt>)</li> 50*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver8.html">Type 8</a> Generic Reference Driver (<tt>PARSE</tt>)</li> 51*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver9.html">Type 9</a> Magnavox MX4200 GPS Receiver (<tt>GPS_MX4200</tt>)</li> 52*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver10.html">Type 10</a> Austron 2200A/2201A GPS Receivers (<tt>GPS_AS2201</tt>)</li> 53*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver11.html">Type 11</a> Arbiter 1088A/B GPS Receiver (<tt>GPS_ARBITER</tt>)</li> 54*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver12.html">Type 12</a> KSI/Odetics TPRO/S IRIG Interface (<tt>IRIG_TPRO</tt>)</li> 55*9c2daa00SOllivier Robert <li class="inline">Type 13 Leitch CSD 5300 Master Clock Controller (<tt>ATOM_LEITCH</tt>)</li> 56*9c2daa00SOllivier Robert <li class="inline">Type 14 EES M201 MSF Receiver (<tt>MSF_EES</tt>)</li> 57*9c2daa00SOllivier Robert <li class="inline">Type 15 reserved</li> 58*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver16.html">Type 16</a> Bancomm GPS/IRIG Receiver (<tt>GPS_BANCOMM</tt>)</li> 59*9c2daa00SOllivier Robert <li class="inline">Type 17 Datum Precision Time System (<tt>GPS_DATUM</tt>)</li> 60*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver18.html">Type 18</a> NIST/USNO/PTB Modem Time Services (<tt>ACTS_MODEM</tt>)</li> 61*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver19.html">Type 19</a> Heath WWV/WWVH Receiver (<tt>WWV_HEATH</tt>)</li> 62*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver20.html">Type 20</a> Generic NMEA GPS Receiver (<tt>NMEA</tt>)</li> 63*9c2daa00SOllivier Robert <li class="inline">Type 21 TrueTime GPS-VME Interface (<tt>GPS_VME</tt>)</li> 64*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver22.html">Type 22</a> PPS Clock Discipline (<tt>PPS</tt>)</li> 65*9c2daa00SOllivier Robert <li class="inline">Type 23 reserved</li> 66*9c2daa00SOllivier Robert <li class="inline">Type 24 reserved</li> 67*9c2daa00SOllivier Robert <li class="inline">Type 25 reserved</li> 68*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver26.html">Type 26</a> Hewlett Packard 58503A GPS Receiver (<tt>GPS_HP</tt>)</li> 69*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver27.html">Type 27</a> Arcron MSF Receiver (<tt>MSF_ARCRON</tt>)</li> 70*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver28.html">Type 28</a> Shared Memory Driver (<tt>SHM</tt>)</li> 71*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver29.html">Type 29</a> Trimble Navigation Palisade GPS (<tt>GPS_PALISADE</tt>)</li> 72*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver30.html">Type 30</a> Motorola UT Oncore GPS <tt>GPS_ONCORE</tt>)</li> 73*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver31.html">Type 31</a> Rockwell Jupiter GPS (<tt>GPS_JUPITER</tt>)</li> 74*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver32.html">Type 32</a> Chrono-log K-series WWVB receiver (<tt>CHRONOLOG</tt>)</li> 75*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver33.html">Type 33</a> Dumb Clock (<tt>DUMBCLOCK</tt>)</li> 76*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver34.html">Type 34</a> Ultralink WWVB Receivers (<tt>ULINK</tt>)</li> 77*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver35.html">Type 35</a> Conrad Parallel Port Radio Clock (<tt>PCF</tt>)</li> 78*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver36.html">Type 36</a> Radio WWV/H Audio Demodulator/Decoder (<tt>WWV</tt>)</li> 79*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver37.html">Type 37</a> Forum Graphic GPS Dating station (<tt>FG</tt>)</li> 80*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver38.html">Type 38</a> hopf GPS/DCF77 6021/komp for Serial Line (<tt>HOPF_S</tt>)</li> 81*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver39.html">Type 39</a> hopf GPS/DCF77 6039 for PCI-Bus (<tt>HOPF_P</tt>)</li> 82*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver40.html">Type 40</a> JJY Receivers (<tt>JJY</tt>)</li> 83*9c2daa00SOllivier Robert <li class="inline">Type 41 TrueTime 560 IRIG-B Decoder</li> 84*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver42.html">Type 42</a> Zyfer GPStarplus Receiver</li> 85*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver43.html">Type 43</a> RIPE NCC interface for Trimble Palisade</li> 86*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver44.html">Type 44</a> NeoClock4X - DCF77 / TDF serial line</li> 87*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver45.html">Type 45</a> Spectracom TSYNC PCI</li> 88*9c2daa00SOllivier Robert <li class="inline"><a href="drivers/driver46.html">Type 46</a> GPSD NG client protocol</li> 89*9c2daa00SOllivier Robert</ul> 90*9c2daa00SOllivier Robert<hr> 91*9c2daa00SOllivier Robert<script type="text/javascript" language="javascript" src="scripts/footer.txt"></script> 92*9c2daa00SOllivier Robert</body> 93*9c2daa00SOllivier Robert</html> 94*9c2daa00SOllivier Robert
