344 lines
13 KiB
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344 lines
13 KiB
HTML
<HTML><HEAD><TITLE>
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Generic Reference Driver
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</TITLE></HEAD><BODY><H3>
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Generic Reference Driver
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</H3><HR>
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<H4>Synopsis</H4>
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Address: 127.127.8.<I>u</I>
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<BR>Reference ID: <TT>PARSE</TT>
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<BR>Driver ID: <TT>GENERIC</TT>
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<BR>Serial Port: <TT>/dev/refclock-<I>u</I></TT>; TTY mode according to
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clock type
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<H4>Description</H4>
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The timecode of these receivers is sampled via a STREAMS module in the
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kernel (The STREAMS module has been designed for use with SUN Systems
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under SunOS 4.1.x or Solaris 2.3 - 2.6. It can be linked directly into
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the kernel or loaded via the loadable driver mechanism). This STREAMS
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module can be adapted to be able to convert different time code formats.
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If the daemon is compiled without the STREAM definition synchronization
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will work without the Sun streams module, though accuracy is
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significantly degraded. This feature allows to use PARSE also on non Sun
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machines.
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<P>The actual receiver status is mapped into various synchronization
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states generally used by receivers. The STREAMS module is configured to
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interpret the time codes of DCF C51, PZF535, PZF509, GPS166, Trimble SV6
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GPS, ELV DCF7000, Schmid, Wharton 400A and low cost receivers (see list
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below).
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<P>The reference clock support in ntp contains the necessary
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configuration tables for those receivers. In addition to supporting
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several different clock types and 4 devices, the generation a a PPS
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signal is also provided as an configuration option. The PPS
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configuration option uses the receiver generated time stamps for feeding
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the PPS loopfilter control for much finer clock synchronization.
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<P>CAUTION: The PPS configuration option is different from the hardware
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PPS signal, which is also supported (see below), as it controls the way
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ntpd is synchronized to the reference clock, while the hardware PPS
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signal controls the way time offsets are determined.
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<P>The use of the PPS option requires receivers with an accuracy of
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better than 1ms.
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<P>Fudge factors
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<P>Only two fudge factors are utilized. The time1 fudge factor defines
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the phase offset of the synchronization character to the actual time. On
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the availability of PPS information the time2 fudge factor defines the
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skew between the PPS time stamp and the receiver timestamp of the PPS
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signal. This parameter is usually zero, as usually the PPS signal is
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believed in time and OS delays should be corrected in the machine
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specific section of the kernel driver. time2 needs only be set when the
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actual PPS signal is delayed for some reason. The flag1 enables input
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filtering. This a median filter with continuous sampling. The flag2
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selects averaging of the samples remaining after the filtering. Leap
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second-handling is controlled with the flag3. When set a leap second
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will be deleted on receipt of a leap second indication from the
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receiver. Otherwise the leap second will be added, (which is the
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default). flag3 should never be set. PPS handling is enabled by adding
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128 to the mode parameter in the server/peer command.
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<P>ntpq (8)
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<P>timecode variable
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<P>The ntpq program can read clock variables command list several
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variables.
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These hold the following information: refclock_time is the local time
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with
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the offset to UTC (format HHMM). The currently active receiver flags are
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listed in refclock_status. Additional feature flags of the receiver are
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optionally listed in parentheses. The actual time code is listed in
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timecode.
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A qualification of the decoded time code format is following in
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refclock_format. The last piece of information is the overall running
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time and the accumulated times for the clock event states in
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refclock_states. When PPS information is present additional variable are
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available. refclock_ppstime lists then the PPS timestamp and
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refclock_ppsskew lists the difference between RS232
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derived timestamp and the PPS timestamp.
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<P>Currently, fourteen clock types (devices /dev/refclock-0 -
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/dev/refclock-3) are supported by the PARSE driver.
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<BR>A note on the implementations:
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<UL><li>These implementations where mainly done <B><I>WITHOUT</I></B>
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actual access to the hardware. Thus not all implementations provide full
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support. The development was done with the help of many souls who had
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the hardware and where so kind to borrow me their time an patience
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during the development and debugging cycle. Thus for continued support
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and quality direct access to the receivers is a big help. Nevertheless i
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am not prepared to buy these reference clocks - donations to <A
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HREF="http://www4.informatik.uni-erlangen.de/~kardel">me</A>
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(<A HREF="mailto: kardel@acm.org">kardel@acm.org</A>) are welcome as
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long as they work within Europe 8-).
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<P>Verified implementations are:
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<UL>
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<LI>
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RAWDCF variants
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<p>These variants are tested for the decoding with my own homegrown
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receivers. Interfacing with specific commercial products may involve
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some fiddeling with cables. Especially commericial RAWDCF receivers have
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a seemingly unlimited number of ways to draw power from the RS232 port
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and to encode the DCF77 datastream. You are mainly on your own here
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unless i have a sample of the receiver.
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<LI>
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<A HREF="http://www.meinberg.de">Meinberg clocks</A>
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<p>These implementations are verified by the Meinberg people themselves
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and i have access to one of these clocks.</UL>
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</UL>
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The pictures below refer to the respective clock and where taken from
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the vendors web pages. They are linked to the respective vendors.
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<UL>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 0</TT></B>
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<p><B><TT><A HREF="http://www.meinberg.de">Meinberg </A>PZF535/<A
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HREF="http://www.meinberg.de/english/pzf509.htm">PZF509 receiver</A> (FM
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demodulation/TCXO / 50us)</TT></B>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 1</TT></B>
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<p><B><TT><A HREF="http://www.meinberg.de">Meinberg </A> PZF535/<A
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HREF="http://www.meinberg.de/english/pzf509.htm">PZF509
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receiver</A> (FM demodulation/OCXO / 50us)</TT></B>
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<BR><A HREF="http://www.meinberg.de/english/pzf509.htm"><IMG
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SRC="pic/pzf509.jpg" ALT="BILD PZF509" HEIGHT=300 WIDTH=260
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ALIGN=TEXTTOP></A>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 2</TT></B>
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<p><B><TT><A HREF="http://www.meinberg.de">Meinberg </A> DCF U/A
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31/<A HREF="http://www.meinberg.de/english/c51.htm">DCF C51 receiver</A>
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(AM demodulation / 4ms)</TT></B>
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<BR><A HREF="http://www.meinberg.de/english/c51.htm"><IMG
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SRC="pic/c51.jpg" ALT="BILD C51" HEIGHT=180 WIDTH=330 ALIGN=TEXTTOP></A>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 3</TT></B>
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<p><B><TT><A HREF="http://www.elv.de">ELV</A> DCF7000 (sloppy AM
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demodulation
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/ 50ms)</TT></B>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 4</TT></B>
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<p><B><TT>Walter Schmid DCF receiver Kit (AM demodulation /
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1ms)</TT></B>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 5</TT></B>
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<p><B><TT>RAW DCF77 100/200ms pulses (Conrad DCF77 receiver module /
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5ms)</TT></B>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 6</TT></B>
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<p><B><TT>RAW DCF77 100/200ms pulses (TimeBrick DCF77 receiver module
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/ 5ms)</TT></B>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 7</TT></B>
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<p><B><TT><A HREF="http://www.meinberg.de">Meinberg </A> <A
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HREF="http://www.meinberg.de/english/gps167.htm">GPS166/GPS167
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receiver</A> (GPS / <<1us)</TT></B>
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<BR><A HREF="http://www.meinberg.de/english/gps167.htm"><IMG
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SRC="pic/gps167.jpg" ALT="BILD GPS167" HEIGHT=300 WIDTH=280
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ALIGN=TEXTTOP></A>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 8</TT></B>
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<p><B><TT><A HREF="http://www.igel.de">IGEL</A> <A
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HREF="http://www.igel.de/eigelmn.htm">clock</A></TT></B>
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<BR><A HREF="http://www.igel.de/eigelmn.htm"><IMG SRC="pic/igclock.gif"
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HEIGHT=174 WIDTH=200></A>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 9</TT></B>
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<p><B><TT><A HREF="http://www.trimble.com">Trimble</A> <A
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HREF="http://www.trimble.com/cgi/omprod.cgi/pd_om011.htm">SVeeSix
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GPS receiver</A>TAIP protocol (GPS / <<1us)</TT></B>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 10</TT></B>
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<p><B><TT><A HREF="http://www.trimble.com">Trimble</A> <A
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HREF="http://www.trimble.com/cgi/omprod.cgi/pd_om011.htm">SVeeSix
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GPS receiver</A> TSIP protocol (GPS / <<1us) (no kernel support
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yet)</TT></B>
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<BR><A HREF="http://www.trimble.com/cgi/omprod.cgi/pd_om011.htm"><IMG
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SRC="pic/pd_om011.gif" ALT="SVeeSix-CM3" BORDER=0 HEIGHT=100 WIDTH=420
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ALIGN=TEXTTOP></A>
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<BR><A HREF="http://www.trimble.com/cgi/omprod.cgi/pd_om006.htm"><IMG
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SRC="pic/pd_om006.gif" ALT="Lassen-SK8" BORDER=0 HEIGHT=100
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WIDTH=420></A>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 11</TT></B>
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<p><B><TT>Radiocode Clocks Ltd RCC 8000 Intelligent Off-Air Master
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Clock
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support </TT></B>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 12</TT></B>
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<p><B><TT><A HREF="http://www.hopf-time.com">HOPF</A> <A
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HREF="http://www.hopf-time.com/kart6021.htm">Funkuhr
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6021</A></TT></B>
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<BR><A HREF="http://www.hopf-time.com/engl/kart6021.htm"><IMG
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SRC="pic/fg6021.gif" ALT="DCF77-Interface Board" HEIGHT=207 WIDTH=238
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ALIGN=TEXTTOP></A>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 13</TT></B>
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<p><B><TT>Diem's Computime Radio Clock</TT></B>
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<BR>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 14</TT></B>
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<p><B><TT>RAWDCF receiver (DTR=high/RTS=low)</TT></B>
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<LI>
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<B><TT>server 127.127.8.0-3 mode 15</TT></B>
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<p><B><TT>WHARTON 400A Series Clocks with a 404.2 Serial
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Interface</TT></B>
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</UL>
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<p>
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Actual data formats and set-up requirements of the various clocks can be
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found in <A HREF="parsedata.htm">NTP PARSE clock data formats</A>.
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<P>The reference clock support carefully monitors the state transitions
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of the receiver. All state changes and exceptional events such as loss
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of time code transmission are logged via the syslog facility. Every hour
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a summary of the accumulated times for the clock states is listed via
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syslog.
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<P>PPS support is only available when the receiver is completely
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synchronized. The receiver is believed to deliver correct time for an
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additional period of time after losing synchronizations, unless a
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disruption in time code transmission is detected (possible power loss).
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The trust period is dependent on the receiver oscillator and thus a
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function of clock type. This is one of the parameters in the clockinfo
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field of the reference clock implementation. This parameter cannot be
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configured by ntpdc.
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<P>In addition to the PPS loopfilter control a true PPS hardware signal
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can be applied on Sun Sparc stations via the CPU serial ports on the CD
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pin. This signal is automatically detected and will be used for offset
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calculation. The input signal must be the time mark for the following
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time code. (The edge sensitivity can be selected - look into the
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appropriate kernel/parsestreams.c for details). Meinberg receivers can
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be connected by feeding the PPS pulse of the receiver via a 1488 level
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converter to Pin 8 (CD) of a Sun serial zs-port. To select PPS support
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the STREAMS driver for PARSE must be loaded and the mode parameter ist
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the mode value of above plus 128. If 128 is not added to the mode value
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PPS will be detected to be available but it will not be used. For PPS to
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be used you MUST add 128 to the mode parameter.
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<P>For the Meinberg GPS166/GPS167 receiver is also a special firmware
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release available (Uni-Erlangen). This release should be used for proper
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operation.
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<P>The raw DCF77 pulses can be fed via a level converter directly into
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Pin 3 (Rx) of the Sun. The telegrams will be decoded an used for
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synchronization. AM DCF77 receivers are running as low as $25. The
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accuracy is dependent on the receiver and is somewhere between 2ms
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(expensive) to 10ms (cheap). Upon bad signal reception of DCF77
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synchronizations will cease as no backup oscillator is available as
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usually found in other reference clock receivers. So it is important to
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have a good place for the DCF77 antenna. For transmitter shutdowns you
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are out of luck unless you have other NTP servers with alternate time
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sources available.
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<H4>Monitor Data</H4>
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Clock states statistics are written hourly the the syslog service.
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Online information can be found by examining the clock variable via the
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ntpq cv command.
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<H4>Fudge Factors</H4>
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<DL>
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<DT><TT>time1 <I>time</I></TT></DT>
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<DD>Specifies the time offset calibration factor, in seconds and
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fraction, with default depending on clock type.</DD>
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<DT><TT>time2 <I>time</I></TT></DT>
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<DD>Specifies the offset if the PPS signal to the actual time. (PPS fine
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tuning).</DD>
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<DT><TT>stratum <I>number</I></TT></DT>
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<DD>Specifies the driver stratum, in decimal from 0 to 15, with default
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0.</DD>
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<DT><TT>refid <I>string</I></TT></DT>
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<DD>Specifies the driver reference identifier, an ASCII string from one
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to four characters, with default according to current clock type.</DD>
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<DT><TT>flag1 0 | 1</TT></DT>
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<DD>Not used by this driver.</DD>
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<DT><TT>flag2 0 | 1</TT></DT>
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<DD>Not used by this driver.</DD>
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<DT><TT>flag3 0 | 1</TT></DT>
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<DD>delete next leap second instead of adding it.</DD>
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<DT>
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<TT>flag4 0 | 1</TT></DT>
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<DD>Delete next leap second instead of adding it - flag will be re-
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defined soon - so don't use it. Statistics are provided by more common
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means (syslog, clock variable via ntpq)</DD>
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</DL>
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<H4>Making your own PARSE clocks</H4>
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The parse clock mechanismis deviated from the way other ntp reference
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clocks work. For a short description how to build parse reference clocks
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see <A HREF="parsenew.htm">making PARSE clocks</A>
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<P>Additional Information
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<P><A HREF="refclock.htm">Reference Clock Drivers</A>
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<hr><a href=index.htm><img align=left src=pic/home.gif></a><address><a
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href="mailto:mills@udel.edu"> David L. Mills <mills@udel.edu></a>
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</address></body></html>
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