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<html><head><title>
Reference Clock Drivers
</title></head><body><h3>
Reference Clock Drivers
</H3>
<IMG ALIGN=LEFT SRC=pic/tardisa.gif>From top:
<UL>
<LI>Austron 2100A GPS Receiver with LORAN-C assist</LI>
<LI>Austron 2000 LORAN-C Receiver></LI>
<LI>Spectracom 8170 WWVB Receiver</LI>
<LI>Hewlett Packard 5061A Cesium Beam Standard</LI>
</UL>
<br clear=left>
The Tardis
<hr>
Support for most of the commonly available radio and modem reference
clocks is included in the default configuration of the NTP daemon for
Unix <TT>ntpd</TT>. Individual clocks can be activated by configuration
file commands, specifically the <TT>server</TT> and <TT>fudge</TT>
commands described in the <A HREF=ntpd.htm><TT>ntpd</TT> program manual
page</A>. The following discussion presents Information on how to select
and configure the device drivers in a running Unix system.
<P>Radio and modem clocks by convention have addresses in the form
127.127.<I>t.u</I>, where <I>t</I> is the clock type and <I>u</I> is a
unit number in the range 0-3 used to distinguish multiple instances of
clocks of the same type. Most of these clocks require support in the
form of a serial port or special bus peripheral, but some can work
directly from the audio codec found in some workstations. The particular
device is normally specified by adding a soft link
<TT>/dev/device<I>u</I></TT> to the particular hardware device involved,
where <I><TT>u</TT></I> correspond to the unit number above.
<p>Most clock drivers communicate with the reference clock using a
serial port, usually at 9600 bps. There are several application program
interfaces (API) used in the various Unix and NT systems, most of which
can be detected at configuration time. Thus, it is important that the
NTP daemon and utilities be compiled on the target system or clone. In
some cases special features are available, such as timestamping in the
kernel or pulse-per-second (PPS) interface. In most cases these features
can be detected at configuration time as well; however, the kernel may
have to be recompiled in order for them to work.
<p>The audio drivers are a special case. These include support for the
NIST time/frequency stations WWV and WWVH, the Canadian time/frequency
station CHU and generic IRIG signals. Currently, support for the Solaris
and SunOS audio API is included in the distribution. It is left to the
volunteer corps to extend this support to other systems. Further
information on hookup, debugging and monitoring is given in the <a
href=audio.htm>Audio Drivers</a> page.
<p>Some drivers depending on longwave and shortwave radio services need
to know the radio propagation time from the transmitter to the receiver,
which can amount to some tens of milliseconds. 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=qth.htm>Stations, Frequencies and Geographic Coordinates</a> page.
Receiver coordinates can be obtained or estimated from various sources.
The actual calculations are beyond the scope of this document.
<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, and features (line
disciplines, etc.). For those drivers without specific documentation,
please contact the author listed in the <A HREF=copyright.htm>Copyright
Notice</A> page.
<P><A HREF=driver1.htm>Type 1</A> Undisciplined Local Clock
(<TT>LOCAL</TT>)
<BR><A HREF=driver2.htm>Type 2</A> Trak 8820 GPS Receiver
(<TT>GPS_TRAK</TT>)
<BR><A HREF=driver3.htm>Type 3</A> PSTI/Traconex 1020 WWV/WWVH
Receiver
(<TT>WWV_PST</TT>)
<BR><A HREF=driver4.htm>Type 4</A> Spectracom WWVB and GPS Receivers
(<TT>WWVB_SPEC</TT>)
<BR><A HREF=driver5.htm>Type 5</A> TrueTime GPS/GOES/OMEGA Receivers
(<TT>TRUETIME</TT>)
<BR><A HREF=driver6.htm>Type 6</A> IRIG Audio Decoder
(<TT>IRIG_AUDIO</TT>)
<BR><A HREF=driver7.htm>Type 7</A> Radio CHU Audio Demodulator/Decoder
(<TT>CHU</TT>)
<BR><A HREF=driver8.htm>Type 8</A> Generic Reference Driver
(<TT>PARSE</TT>)
<BR><A HREF=driver9.htm>Type 9</A> Magnavox MX4200 GPS Receiver
(<TT>GPS_MX4200</TT>)
<BR><A HREF=driver10.htm>Type 10</A> Austron 2200A/2201A GPS Receivers
(<TT>GPS_AS2201</TT>)
<BR><A HREF=driver11.htm>Type 11</A> Arbiter 1088A/B GPS Receiver
(<TT>GPS_ARBITER</TT>)
<BR><A HREF=driver12.htm>Type 12</A> KSI/Odetics TPRO/S IRIG Interface
(<TT>IRIG_TPRO</TT>)
<BR>Type 13 Leitch CSD 5300 Master Clock Controller
(<TT>ATOM_LEITCH</TT>)
<BR>Type 14 EES M201 MSF Receiver (<TT>MSF_EES</TT>)
<BR><A HREF=driver5.htm>Type 15</A> * TrueTime generic receivers
<BR>Type 16 Bancomm GPS/IRIG Receiver (<TT>GPS_BANCOMM</TT>)
<BR>Type 17 Datum Precision Time System (<TT>GPS_DATUM</TT>)
<BR><A HREF=driver18.htm>Type 18</A> NIST Modem Time Service
(<TT>ACTS_NIST</TT>)
<BR><A HREF=driver19.htm>Type 19</A> Heath WWV/WWVH Receiver
(<TT>WWV_HEATH</TT>)
<BR><A HREF=driver20.htm>Type 20</A> Generic NMEA GPS Receiver
(<TT>NMEA</TT>)
<BR>Type 21 TrueTime GPS-VME Interface (<TT>GPS_VME</TT>)
<BR><A HREF=driver22.htm>Type 22</A> PPS Clock Discipline
(<TT>PPS</TT>)
<BR><A HREF=driver23.htm>Type 23</A> PTB Modem Time Service
(<TT>ACTS_PTB</TT>)
<BR><A HREF=driver24.htm>Type 24</A> USNO Modem Time Service
(<TT>ACTS_USNO</TT>)
<BR><A HREF=driver5.htm>Type 25</A> * TrueTime generic receivers
<BR><A HREF=driver26.htm>Type 26</A> Hewlett Packard 58503A GPS
Receiver (<TT>GPS_HP</TT>)
<BR><A HREF=driver27.htm>Type 27</A> Arcron MSF Receiver
(<TT>MSF_ARCRON</TT>)
<BR><A HREF=driver28.htm>Type 28</A> Shared Memory Driver
(<TT>SHM</TT>)
<BR><A HREF=driver29.htm>Type 29</A> Trimble Navigation Palisade GPS
(<TT>GPS_PALISADE</TT>)
<BR><A HREF=driver30.htm>Type 30</A> Motorola UT Oncore GPS
(<TT>GPS_ONCORE</TT>)
<BR>Type 31 Rockwell Jupiter GPS (<TT>GPS_JUPITER</TT>)
<BR><A HREF=driver34.htm>Type 34</A> Ultralink WWVB Receivers
<BR><A HREF=driver35.htm>Type 35</A> Conrad Parallel Port Radio Clock
(<TT>PCF</TT>)
<BR><A HREF=driver36.htm>Type 36</A> Radio WWV/H Audio
Demodulator/Decoder(<TT>WWV</TT>)
<BR><A HREF=driver37.htm>Type 37</A> Forum Graphic GPS Dating station
(<TT>FG</TT>)
<P>* All TrueTime receivers are now supported by one driver, type 5.
Types 15 and 25 will be retained only for a limited time and may be
reassigned in future.
<P>Additional Information
<P><A HREF=prefer.htm>Mitigation Rules and the <TT>prefer</TT>
Keyword</A>
<BR><A HREF=rdebug.htm>Debugging Hints for Reference Clock Drivers</A>
<BR><A HREF=ldisc.htm>Line Disciplines and Streams Drivers</A>
<BR><A HREF=audio.htm>Reference Clock Audio Drivers</A>
<BR><A HREF=pps.htm>Pulse-per-second (PPS) Signal Interfacing</A>
<BR><A HREF=howto.htm>How To Write a Reference Clock Driver</A>
<BR><A HREF=index.htm>The Network Time Protocol (NTP)
Distribution </A>
<hr><a href=index.htm><img align=left src=pic/home.gif></a><address><a
href=mailto:mills@udel.edu> David L. Mills <mills@udel.edu></a>
</address></a></body></html>
|
