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diff --git a/contrib/ntp/html/driver22.htm b/contrib/ntp/html/driver22.htm deleted file mode 100644 index a293cbc..0000000 --- a/contrib/ntp/html/driver22.htm +++ /dev/null @@ -1,159 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"> -<html> -<head> -<meta name="generator" content="HTML Tidy, see www.w3.org"> -<title>PPS Clock Discipline</title> -</head> -<body> -<h3>PPS Clock Discipline</h3> - -<hr> -<h4>Synopsis</h4> - -Address: 127.127.22.<i>u</i> <br> -Reference ID: <tt>PPS</tt> <br> -Driver ID: <tt>PPS</tt> <br> -Serial or Parallel Port: <tt>/dev/pps<i>u</i></tt> <br> -Requires: PPSAPI interface - -<p>Note: This driver supersedes an older one of the same name. The -older driver operated with several somewhat archaic signal -interface devices, required intricate configuration and was poorly -documented. This driver operates only with the PPSAPI interface -proposed as an IETF standard. Note also that the <tt>pps</tt> -configuration command has been obsoleted by this driver.</p> - -<h4>Description</h4> - -<p>This driver furnishes an interface for the pulse-per-second -(PPS) produced by a cesium clock, radio clock or related equipment. -It can be used to augment the serial timecode generated by a GPS -receiver, for example. It can be used to remove accumulated jitter -and re-time a secondary server when synchronized to a primary -server over a congested, wide-area network and before -redistributing the time to local clients. The driver includes -extensive signal sanity checks and grooming algorithms. A range -gate and frequency discriminator reject noise and signals with -incorrect frequency. A multiple-stage median filter rejects jitter -due to hardware interrupt and operating system latencies. A -trimmed-mean algorithm determines the best time samples. With -typical workstations and processing loads, the incidental jitter -can be reduced to less than a microsecond.</p> - -<p>While this driver can discipline the time and frequency relative -to the PPS source, it cannot number the seconds. For this purpose a -auxiliary source is required, ordinarily a radio clock operated as -a primary reference (stratum 1) source; however, another NTP time -server can be used as well. For this purpose, the auxiliary source -is marked as the prefer peer, as described in the <a href= -"prefer.htm">Mitigation Rules and the <tt>prefer</tt> Keyword</a> -page.</p> - -<p>The driver requires the PPSAPI interface<sup>1</sup>, which is a -proposed IETF standard. The interface consists of the <tt> -timepps.h</tt> header file and associated kernel support. Support -for this interface is included in current versions of FreeBSD and -Linux and proprietary versions for Digital/Compaq Tru64 (Alpha), -Sun Solaris and Sun SunOS. See the <a href="pps.htm"> -Pulse-per-second (PPS) Signal Interfacing</a> page for further -information.</p> - -<p>The PPS source can be connected via a serial or parallel port, -depending on the hardware and operating system. The port can be -dedicated to the PPS source or shared with another device. A radio -clock is usually connected via a serial port and the PPS source -connected via a level converter to the data carrier detect (DCD) -pin (DB-9 pin 1, DB-25 pin 8) of the same connector. In some -systems where a parallel port and driver are available, the PPS -signal can be connected directly to the ACK pin (pin 10) of the -connector. Whether the PPS signal is connected via a dedicated port -or shared with another device, the driver opens the device <tt> -/dev/pps%d</tt>, where <tt>%d</tt> is the unit number. As with -other drivers, links can be used to redirect the logical name to -the actual physical device.</p> - -<p>The driver normally operates like any other driver and uses the -same mitigation algorithms and PLL/FLL clock discipline -incorporated in the daemon. If kernel PLL/FLL support is available, -the kernel PLL/FLL clock discipline is used instead. The default -behavior is not to use the kernel PPS clock discipline, even if -present. This driver incorporates a good deal of signal processing -to reduce jitter using the median filter and trimmed average -algorithms in the driver interface. As the result, performance with -minpoll and maxpoll configured at the minimum 4 (16s) is generally -better than the kernel PPS clock discipline. However, fudge flag 3 -can be used to enable this discipline if necessary.</p> - -<p>Note that the PPS source is considered reachable only if the -auxiliary source is the prefer peer, is reachable and is selected -to discipline the system clock. The stratum assigned to the PPS -source is automatically determined. If the auxiliary source is -unreachable or inoperative, the stratum is set to 16; otherwise it -is set to match the stratum of the auxiliary source. Since the -stratum is determined dynamically, it is not possible to assign -another stratum using the <tt>fudge</tt> command as in other -drivers.</p> - -<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></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>PPS</tt>.</dd> - -<dt><tt>flag1 0 | 1</tt></dt> - -<dd>Not used by this driver.</dd> - -<dt><tt>flag2 0 | 1</tt></dt> - -<dd>Specifies the PPS signal on-time edge: 0 for assert (default), -1 for clear.</dd> - -<dt><tt>flag3 0 | 1</tt></dt> - -<dd>Controls the kernel PPS discipline: 0 for disable (default), 1 -for enable.</dd> - -<dt><tt>flag4 0 | 1</tt></dt> - -<dd>Not used by this driver.</dd> -</dl> - -<p>Additional Information</p> - -<p><a href="refclock.htm">Reference Clock Drivers</a></p> - -<p>Reference</p> - -<ol> -<li>Mogul, J., D. Mills, J. Brittenson, J. Stone and U. Windl. -Pulse-per-second API for Unix-like operating systems, version 1. -Request for Comments RFC-2783, Internet Engineering Task Force, -March 2000, 31 pp.</li> -</ol> - -<hr> -<a href="index.htm"><img align="left" src="pic/home.gif" alt= -"gif"></a> - -<address><a href="mailto:mills@udel.edu">David L. Mills -<mills@udel.edu></a></address> -</body> -</html> - |
