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diff --git a/contrib/ntp/html/driver4.htm b/contrib/ntp/html/driver4.htm new file mode 100644 index 0000000..4f3abd7 --- /dev/null +++ b/contrib/ntp/html/driver4.htm @@ -0,0 +1,126 @@ +<HTML><HEAD><TITLE> +Spectracom 8170 and Netclock/2 WWVB Receivers +</TITLE></HEAD><BODY><H3> +Spectracom 8170 and Netclock/2 WWVB Receivers +</H3><HR> + +<H4>Synopsis</H4> + +Address: 127.127.4.<I>u</I> +<BR>Reference ID: <TT>WWVB</TT> +<BR>Driver ID: <TT>WWVB_SPEC</TT> +<BR>Serial Port: <TT>/dev/wwvb<I>u</I></TT>; 9600 baud, 8-bits, no +parity +<BR>Features: <TT>tty_clk</TT> + +<H4>Description</H4> + +This driver supports all known Spectracom radio and satellite clocks, +including the Model 8170 and Netclock/2 WWVB Synchronized Clocks and the +Netclock/GPS GPS Master Clock. The claimed accuracy of the WWVB clocks +is 100 usec relative to the broadcast signal. These clocks have proven a +reliable source of time, except in some parts of the country with high +levels of conducted RF interference. WIth the GPS clock the claimed +accuracy is 130 ns. However, in most cases the actual accuracy is +limited by the precision of the timecode and the latencies of the serial +interface and operating system. + +<P>The DIPswitches on these clocks should be set to 24-hour display, +AUTO DST off, data format 0 or 2 (see below) and baud rate 9600. If this +clock is used as the source for the IRIG Audio Decoder +(<tt>refclock_irig.c</tt> in this distribution), set the DIPswitches for +AM IRIG output and IRIG format 1 (IRIG B with signature control). + +<P>There are two timecode formats used by these clocks. Format 0, which +is available with all clocks, and format 2, which is available with all +clocks except the original (unmodified) Model 8170. + +<P>Format 0 (22 ASCII printing characters): +<br><cr><lf>i ddd hh:mm:ss TZ=zz<cr><lf> + +<p>on-time = first <cr> +<br>i = synchronization flag (' ' = in synch, '?' = out synch) +<br>hh:mm:ss = hours, minutes, seconds</PRE> + +<p>The alarm condition is indicated by other than ' ' at <TT>i</TT>, +which occurs during initial synchronization and when received signal is +lost for about ten hours. + +<P>Format 2 (24 ASCII printing characters): +<br>lt;cr>lf>iqyy ddd hh:mm:ss.fff ld + +<p>on-time = <cr> +<br>i = synchronization flag (' ' = in synch, '?' = out synch) +<br>q = quality indicator (' ' = locked, 'A'...'D' = unlocked) +<br>yy = year (as broadcast) +<br>ddd = day of year +<br>hh:mm:ss.fff = hours, minutes, seconds, milliseconds</PRE> + +<p>The alarm condition is indicated by other than ' ' at <TT>i</TT>, +which occurs during initial synchronization and when received signal is +lost for about ten hours. The unlock condition is indicated by other +than ' ' at <TT>q</TT>. + +<P>The <TT>q</TT> is normally ' ' when the time error is less than 1 ms +and a character in the set <TT>A...D</TT> when the time error is less +than 10, 100, 500 and greater than 500 ms respectively. The <TT>l</TT> +is normally ' ', but is set to <TT>L</TT> early in the month of an +upcoming UTC leap second and reset to ' ' on the first day of the +following month. The <TT>d</TT> is set to <TT>S</TT> for standard time +<TT>S</TT>, <TT>I</TT> on the day preceding a switch to daylight time, +<TT>D</TT> for daylight time and <TT>O</TT> on the day preceding a +switch to standard time. The start bit of the first +<cr> is synchronized to the indicated time as returned. + +<P>This driver does not need to be told which format is in use - it +figures out which one from the length of the message. A three-stage +median filter is used to reduce jitter and provide a dispersion measure. +The driver makes no attempt to correct for the intrinsic jitter of the +radio itself, which is a known problem with the older radios. + +<H4>Monitor Data</H4> + +The driver writes each timecode as received to the <TT>clockstats</TT> +file. When enabled by the <TT>flag4</TT> fudge flag, a table of quality +data maintained internally by the Netclock/2 is retrieved and written to +the <TT>clockstats</TT> file when the first timecode message of a new +dayis received. + +<H4>Fudge Factors</H4> + +<DL> + +<DT><TT>time1 <I>time</I></TT></DT> +<DD>Specifies the time offset calibration factor, in seconds and +fraction, +with default 0.0.</DD> + +<DT><TT>time2 <I>time</I></TT></DT> +<DD>Not used by this driver.</DD> + +<DT><TT>stratum <I>number</I></TT></DT> +<DD>Specifies the driver stratum, in decimal from 0 to 15, with default +0.</DD> + +<DT><TT>refid <I>string</I></TT></DT> +<DD>Specifies the driver reference identifier, an ASCII string from one +to four characters, with default <TT>WWVB</TT>.</DD> + +<DT><TT>flag1 0 | 1</TT></DT> +<DD>Not used by this driver.</DD> + +<DT><TT>flag2 0 | 1</TT></DT> +<DD>Not used by this driver.</DD> + +<DT><TT>flag3 0 | 1</TT></DT> +<DD>Not used by this driver.</DD> + +<DT><TT>flag4 0 | 1</TT></DT> +<DD>Enable verbose <TT>clockstats</TT> recording if set.</DD> + +</DL> + +Additional Information + +<P><A HREF="refclock.htm">Reference Clock Drivers</A> +<HR><ADDRESS>David L. Mills (mills@udel.edu)</ADDRESS></BODY></HTML> |
