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diff --git a/contrib/ntp/html/driver2.htm b/contrib/ntp/html/driver2.htm new file mode 100644 index 0000000..885a1b2 --- /dev/null +++ b/contrib/ntp/html/driver2.htm @@ -0,0 +1,137 @@ +<HTML> +<HEAD> + <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> + <META NAME="GENERATOR" CONTENT="Mozilla/4.01 [en] (Win95; I) [Netscape]"> + <TITLE>Trak 8820 GPS Receiver +</TITLE> +</HEAD> +<BODY> + +<H3> +Trak 8820 GPS Receiver</H3> + +<HR> +<H4> +Synopsis</H4> +Address: 127.127.2.<I>u</I> +<BR>Reference ID: <TT>GPS</TT> +<BR>Driver ID: <TT>GPS_TRAK</TT> +<BR>Serial Port: <TT>/dev/trak<I>u</I></TT>; 9600 baud, 8-bits, no parity +<BR>Features: <TT>tty_clk</TT> +<H4> +Description</H4> +This driver supports the Trak 8820 GPS Station Clock. The claimed accuracy +at the 1-PPS output is 200-300 ns relative to the broadcast signal; 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>For best accuracy, this radio requires the <TT>tty_clk</TT> line discipline, +which captures a timestamp at the <TT>*</TT> on-time character of the timecode. +Using this discipline the jitter is in the order of 1 ms and systematic +error about 0.5 ms. If unavailable, the buffer timestamp is used, which +is captured at the <TT>\r</TT> ending the timecode message. This introduces +a systematic error of 23 character times, or about 24 ms at 9600 bps, together +with a jitter well over 8 ms on Sun IPC-class machines. + +<P>Using the menus, the radio should be set for 9600 bps, one stop bit +and no parity. It should be set to operate in computer (no echo) mode. +The timecode format includes neither the year nor leap-second warning. + +<P>In operation, this driver sends a <TT>RQTS\r</TT> request to the radio +at initialization in order to put it in continuous time output mode. The +radio then sends the following message once each second: +<PRE>*RQTS U,ddd:hh:mm:ss.0,q<cr><lf> + +on-time = '*' +ddd = day of year +hh:mm:ss = hours, minutes, seconds +q = quality indicator (phase error), 0-6: + 0 > 20 us + 6 > 10 us + 5 > 1 us + 4 > 100 ns + 3 > 10 ns + 2 < 10 ns</PRE> +The alarm condition is indicated by <TT>0</TT> at <TT>Q</TT>, which means +the radio has a phase error greater than 20 us relative to the broadcast +time. The absence of year, DST and leap-second warning in this format is +also alarmed. + +<P>The continuous time mode is disabled using the <TT>RQTX\r</TT> request, +following which the radio sends a <TT>RQTX DONE<cr><lf></TT> response. +In the normal mode, other control and status requests are effective, including +the leap-second status request <TT>RQLS<cr></TT>. The radio responds +with <TT>RQLS yy,mm,dd<cr><lf></TT>, where <TT>yy,mm,dd</TT> are +the year, month and day. Presumably, this gives the epoch of the next leap +second, <TT>RQLS 00,00,00</TT> if none is specified in the GPS message. +Specified in this form, the information is generally useless and is ignored +by the driver. +<H4> +Monitor Data</H4> +When enabled by the <TT>flag4</TT> fudge flag, every received timecode +is written as-is to the <TT>clockstats</TT> file. +<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>GPS</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> + + +<P>Additional Information + +<P><A HREF="refclock.htm">Reference Clock Drivers</A></DL> + +<HR> +<ADDRESS> +David L. Mills (mills@udel.edu)</ADDRESS> + +</BODY> +</HTML> |
