134 lines
4.8 KiB
HTML
134 lines
4.8 KiB
HTML
<!-- $NetBSD: driver4.html,v 1.1 1998/12/30 20:20:34 mcr Exp $ -->
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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML Strict//EN">
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<html><head><title>
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Spectracom 8170 and Netclock/2 WWVB Receivers
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</title></head><body><h3>
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Spectracom 8170 and Netclock/2 WWVB Receivers
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</h3><hr>
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<p><h4>Synopsis</h4>
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<p>Address: 127.127.4.<var>u</var>
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<br>Reference ID: WWVB
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<br>Driver ID: WWVB-SPEC
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<br>Serial Port: <code>/dev/wwvb<var>u</var></code>; 9600 baud, 8-bits,
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no parity
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<br>Features: <code>tty_clk</code>
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<p><h4>Description</h4>
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<p>This driver supports the Spectracom Model 8170 and Netclock/2 WWVB
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Synchronized Clock. This clock has proven a reliable source of time,
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except in some cases of high ambient conductive RF interference. The
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claimed accuracy of the clock is 100 usec relative to the broadcast
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signal; however, in most cases the actual accuracy is limited by the
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precision of the timecode and the latencies of the serial interface and
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operating system.
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<p>The DIPswitches on this clock should be set to 24-hour display, AUTO
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DST off, data format 0 or 2 (see below) and baud rate 9600.
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If this clock is to used as the source for the IRIG Audio Decoder
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(refclock_irig.c in this distribution), set the DIPswitches for AM IRIG
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output and IRIG format 1 (IRIG B with signature control).
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<p>There are two timecode formats used by these clocks. Format 0, which
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is available with both the Netclock/2 and 8170, and format 2, which is
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available only with the Netclock/2 and specially modified 8170.
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<p>Format 0 (22 ASCII printing characters):
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<pre>
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<cr><lf>i ddd hh:mm:ss TZ=zz<cr><lf>
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on-time = first <cr>
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i = synchronization flag (' ' = in synch, '?' = out synch)
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hh:mm:ss = hours, minutes, seconds
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</pre>
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<p>The alarm condition is indicated by other than ' ' at <code>i</code>,
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which occurs during initial synchronization and when received signal is
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lost for about ten hours.
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<p>Format 2 (24 ASCII printing characters):
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<pre>
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<cr><lf>iqyy ddd hh:mm:ss.fff ld
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on-time = <cr>
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i = synchronization flag (' ' = in synch, '?' = out synch)
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q = quality indicator (' ' = locked, 'A'...'D' = unlocked)
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yy = year (as broadcast)
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ddd = day of year
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hh:mm:ss.fff = hours, minutes, seconds, milliseconds
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</pre>
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<p>The alarm condition is indicated by other than ' ' at <code>i</code>,
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which occurs during initial synchronization and when received signal is
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lost for about ten hours. The unlock condition is indicated by other
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than ' ' at <code>q</code>.
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<p>The <code>q</code> is normally ' ' when the time error is less than 1
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ms and a character in the set <code>A...D</code> when the time error is
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less than 10, 100, 500 and greater than 500 ms respectively. The
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<code>l</code> is normally ' ', but is set to <code>L</code> early in
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the month of an upcoming UTC leap second and reset to ' ' on the first
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day of the following month. The <code>d</code> is set to <code>S</code>
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for standard time <code>S</code>, <code>I</code> on the day preceding a
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switch to daylight time, <code>D</code> for daylight time and
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<code>O</code> on the day preceding a switch to standard time. The start
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bit of the first <cr> is synchronized to the indicated time as
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returned.
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<p>This driver does not need to be told which format is in use - it
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figures out which one from the length of the message. A three-stage
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median filter is used to reduce jitter and provide a dispersion measure.
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The driver makes no attempt to correct for the intrinsic jitter of the
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radio itself, which is a known problem with the older radios.
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<p><h4>Monitor Data</h4>
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<p>The driver writes each timecode as received to the
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<code>clockstats</code> file. When enabled by the <code>flag4</code>
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fudge flag, a table of quality data maintained internally by the
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Netclock/2 is retrieved and written to the <code>clockstats</code> file
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when the first timecode message of a new day is received.
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<p><h4>Fudge Factors</h4>
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<dl>
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<dt><code>time1 <i>time</i></code>
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<dd>Specifies the time offset calibration factor, in seconds and
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fraction, with default 0.0. For a calibrated Sun IPC, the correct value
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is about .0048.
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<p><dt><code>time2 <i>time</i></code>
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<dd>Not used by this driver.
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<p><dt><code>stratum <i>number</i></code>
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<dd>Specifies the driver stratum, in decimal from 0 to 15, with default
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0.
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<p><dt><code>refid <i>string</i></code>
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<dd>Specifies the driver reference identifier, an ASCII string from one
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to four characters, with default <code>WWVB</code>.
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<p><dt><code>flag1 0 | 1</code>
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<dd>Not used by this driver.
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<p><dt><code>flag2 0 | 1</code>
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<dd>Not used by this driver.
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<p><dt><code>flag3 0 | 1</code>
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<dd>Enable <code>ppsclock</code> line discipline/streams module if set.
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<p><dt><code>flag4 0 | 1</code>
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<dd>Enable extended <code>clockstats</code> recording if set.
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</dl>
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<p>Additional Information
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<p><a href="refclock.html"> Reference Clock Drivers</a>
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<hr><address>David L. Mills (mills@udel.edu)</address></body></html>
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