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