</head>
<body>
<h3>NIST/USNO/PTB Modem Time Services</h3>
-<p>Autjhor: David L. Mills (mills@udel.edu)<br>
+<p>Author: David L. Mills (mills@udel.edu)<br>
Last update:
<!-- #BeginDate format:En2m -->03-Sep-2010 17:59<!-- #EndDate -->
UTC</p>
<p>There are three modes of operation selected by the <tt>mode</tt> keyword in the <tt>server</tt> configuration command. In manual mode (2) the calling program is initiated by setting fudge <tt>flag1</tt>. This can be done manually using <tt>ntpdc</tt>, or by a cron job. In auto mode (0) <tt>flag1</tt> is set at each poll event. In backup mode (1) <tt>flag1</tt> is set at each poll event, but only if no other synchronization sources are available.</p>
<p>When <tt>flag1</tt> is set, the calling program dials the first number in the list specified by the <tt>phone</tt> command. If the call fails for any reason, the program dials the second number and so on. The phone number is specified by the Hayes ATDT prefix followed by the number itself, including the prefix and long-distance digits and delay code, if necessary. The <tt>flag1</tt> is reset and the calling program terminated if (a) valid clock update has been determined, (b) no more numbers remain in the list, (c) a device fault or timeout occurs or (d) fudge <tt>flag1</tt> is reset manually using <tt>ntpdc</tt>.</p>
<p>The driver automatically recognizes the message format of each modem time service. It selects the parsing algorithm depending on the message length. There is some hazard should the message be corrupted. However, the data format is checked carefully and only if all checks succeed is the message accepted. Corrupted lines are discarded without complaint. Once the service is known, the reference identifier for the driver is set to NIST, USNO, PTB or WWVB as appropriate.</p>
-<p>Ordinarily, the serial port is connected to a modem; however, if fudge <tt>flag3</tt> is set, it can be connected directly to a Spectracom WWV or GPS radio for testing or calibration. The Spectracom radio can be connected via a modem if the radio is connfigured to send time codes continuoulsly at 1-s intervals. In principle, fudge <tt>flag2</tt> enables port locking, allowing the modem to be shared when not in use by this driver. At least on Solaris with the current NTP I/O routines, this results in lots of ugly error messages.</p>
+<p>The Spectracom radio can be connected via a modem if the radio is configured to send time codes continuously at 1-s intervals. In principle, fudge <tt>flag2</tt> enables port locking, allowing the modem to be shared when not in use by this driver. At least on Solaris with the current NTP I/O routines, this results in lots of ugly error messages.</p>
<p>The <tt>minpoll</tt> and <tt>maxpoll</tt> keywords of the server configuration command can be used to limit the intervals between calls. The recommended settings are 12 (1.1 hours) for <tt>minpoll</tt> and 17 (36 hours) for <tt>maxpoll</tt>. Ordinarily, the poll interval will start at <tt>minpoll</tt> and ramp up to <tt>maxpoll</tt> in a day or two.</p>
<h4>US Phone Numbers and Formats</h4>
<p>Note: Phone numbers include the entire Hayes modem command, including the <tt>ATDT</tt> and other control codes as may be necessary. For most cases only the <tt>ATDT</tt> may be necessary.</p>
<p><a href="http://www.spectracomcorp.com">Spectracom GPS and WWVB Receivers</a></p>
<p>If a modem is connected to a Spectracom receiver, this driver will call it and retrieve the time in one of two formats, 0 and 2. Ordinarily, the receiver requires a <tt>T</tt> in order to return the timecode. As this driver does not send data via the modem, it must either be configured in continuous mode or be polled by another local driver.</p>
<h4>Monitor Data</h4>
-<p>The received timecode is written as-is to the <tt>clockstats</tt> file along with the Hayes connection and hangup commands and result codes.</p>
+<p>The received timecode is written as-is to the <tt>clockstats</tt> file along with the Hayes connection and hang-up commands and result codes.</p>
<h4>Fudge Factors</h4>
<dl>
<dt><tt>time1 <i>time</i></tt></dt>
<dt><tt>flag2 0 | 1</tt></dt>
<dd>Enables port locking if 1, disables if 0 (default).</dd>
<dt><tt>flag3 0 | 1</tt></dt>
- <dd>Enables direct connection if 1, or modem if 0 (default). If set, the driver will send a single character 'T' at every poll event.</dd>
+ <dd>Not used by this driver.</dd>
<dt><tt>flag4 0 | 1</tt></dt>
<dd>Not used by this driver.</dd>
</dl>
projects / thirdparty / ntp.git / commitdiff
