110 lines
3.0 KiB
HTML
110 lines
3.0 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>Hewlett Packard 58503A GPS 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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Hewlett Packard 58503A GPS Receiver</H3>
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<HR>
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<H4>
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Synopsis</H4>
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Address: 127.127.26.<I>u</I>
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<BR>Reference ID: <TT>GPS</TT>
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<BR>Driver ID: <TT>GPS_HP</TT>
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<BR>Serial Port: <TT>/dev/hpgps<I>u</I></TT>; 9600 baud, 8-bits, no parity
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<H4>
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Description</H4>
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This driver supports the HP 58503A Time and Frequency Reference Receiver.
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It uses HP SmartClock (TM) to implement an Enhanced GPS receiver. The receiver
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accuracy when locked to GPS in normal operation is better than 1 usec.
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The accuracy when operating in holdover is typically better than 10 us
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per day. It receiver should be operated with factory default settings.
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Initial driver operation: expects the receiver to be already locked to
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GPS, configured and able to output timecode format 2 messages.
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<P>The driver uses the poll sequence <TT>:PTIME:TCODE?</TT> to get a response
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from the receiver. The receiver responds with a timecode string of ASCII
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printing characters, followed by a <cr><lf>, followed by a prompt
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string issued by the receiver, in the following format:
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<PRE>T#yyyymmddhhmmssMFLRVcc<cr><lf></PRE>
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The driver processes the response at the <cr> and <lf><cr> and
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<lf>, so what the driver sees is the prompt from the previous poll,
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followed by this timecode. The prompt from the current poll is (usually)
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left unread until the next poll. So (except on the very first poll) the
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driver sees this:
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<PRE>T#yyyymmddhhmmssMFLRVcc<cr><lf></PRE>
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The T is the on-time character, at 980 msec. before the next 1PPS edge.
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The # is the timecode format type. We look for format 2. Without any of
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the CLK or PPS stuff, then, the receiver buffer timestamp at the <cr>y
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is 24 characters later, which is about 25 msec. at 9600 bps, so the first
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approximation for fudge time1 is nominally -0.955 seconds. This number
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probably needs adjusting for each machine / OS type, so far: -0.955000
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on an HP 9000 Model 712/80 HP-UX 9.05 -0.953175 on an HP 9000 Model 370
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HP-UX 9.10
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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>GPS</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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<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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