125 lines
3.5 KiB
HTML
125 lines
3.5 KiB
HTML
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<HTML>
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<HEAD>
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
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<META NAME="GENERATOR" CONTENT="Mozilla/4.01 [en] (Win95; I) [Netscape]">
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<TITLE>Heath WWV/WWVH Receiver
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</TITLE>
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</HEAD>
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<BODY>
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<H3>
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Heath WWV/WWVH Receiver</H3>
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<HR>
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<H4>
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Synopsis</H4>
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Address: 127.127.19.<I>u</I>
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<BR>Reference ID: <TT>WWV</TT>
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<BR>Driver ID: <TT>WWV_HEATH</TT>
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<BR>Serial Port: <TT>/dev/heath<I>u</I></TT>; 1200 baud, 8-bits, no parity
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<BR>Features: <TT>tty_clk</TT>
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<BR>Requires: <TT>/usr/include/sys/termios.h</TT> header file with modem
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control
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<H4>
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Description</H4>
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This driver supports the Heath GC-1000 Most Accurate Clock, with RS232C
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Output Accessory. This is a WWV/WWVH receiver somewhat less robust than
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other supported receivers. Its claimed accuracy is 100 ms when actually
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synchronized to the broadcast signal, but this doesn't happen even most
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of the time, due to propagation conditions, ambient noise sources, etc.
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When not synchronized, the accuracy is at the whim of the internal clock
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oscillator, which can wander into the sunset without warning. Since the
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indicated precision is 100 ms, expect a host synchronized only to this
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thing to wander to and fro, occasionally being rudely stepped when the
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offset exceeds the default CLOCK_MAX of 128 ms.
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<P>The internal DIPswitches should be set to operate at 1200 baud in MANUAL
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mode and the current year. The external DIPswitches should be set to GMT
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and 24-hour format. It is very important that the year be set correctly
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in the DIPswitches; otherwise, the day of year will be incorrect after
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28 April of a normal or leap year.
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<P>In MANUAL mode the clock responds to a rising edge of the request to
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send (RTS) modem control line by sending the timecode. Therefore, it is
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necessary that the operating system implement the <TT>TIOCMBIC</TT> and
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<TT>TIOCMBIS</TT> ioctl system calls and <TT>TIOCM_RTS</TT> control bit.
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Present restrictions require the use of a POSIX-compatible programming
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interface, although other interfaces may work as well.
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<P>The clock message consists of 23 ASCII printing characters in the following
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format:
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<PRE>hh:mm:ss.f dd/mm/yr<cr>
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hh:mm:ss.f = hours, minutes, seconds
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f = deciseconds ('?' when out of spec)
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dd/mm/yr = day, month, year</PRE>
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The alarm condition is indicated by '?', rather than a digit, at A. Note
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that 0?:??:??.? is displayed before synchronization is first established
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and hh:mm:ss.? once synchronization is established and then lost again
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for about a day.
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<P>A fudge time1 value of .07 s appears to center the clock offset residuals.
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<H4>
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Fudge Factors</H4>
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<DL>
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<DT>
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<TT>time1 <I>time</I></TT></DT>
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<DD>
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Specifies the time offset calibration factor, in seconds and fraction,
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with default 0.0.</DD>
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<DT>
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<TT>time2 <I>time</I></TT></DT>
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<DD>
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Not used by this driver.</DD>
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<DT>
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<TT>stratum <I>number</I></TT></DT>
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<DD>
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Specifies the driver stratum, in decimal from 0 to 15, with default 0.</DD>
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<DT>
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<TT>refid <I>string</I></TT></DT>
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<DD>
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Specifies the driver reference identifier, an ASCII string from one to
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four characters, with default <TT>WWV</TT>.</DD>
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<DT>
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<TT>flag1 0 | 1</TT></DT>
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<DD>
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Not used by this driver.</DD>
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<DT>
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<TT>flag2 0 | 1</TT></DT>
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<DD>
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Not used by this driver.</DD>
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<DT>
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<TT>flag3 0 | 1</TT></DT>
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<DD>
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Not used by this driver.</DD>
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<DT>
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<TT>flag4 0 | 1</TT></DT>
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<DD>
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Not used by this driver</DD>
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</DL>
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Additional Information
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<P><A HREF="refclock.htm">Reference Clock Drivers</A>
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<HR>
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<ADDRESS>
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David L. Mills (mills@udel.edu)</ADDRESS>
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</BODY>
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</HTML>
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