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= Arbiter 1088A/B GPS Receiver =
= Arbiter 1088A/B GPS Receiver
include::html.include[]
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: arbiter
......@@ -10,7 +10,7 @@ Driver ID: GPS_ARBITER
Serial Port: /dev/gps__u__; 9600bps 8N1
Features: tty_clk
== Deprecation warning ==
== Deprecation warning
This refclock is deprecated and obsolete. The NTPsec maintainers plan
to remove it in a future release. If you have a requirement for it,
......@@ -21,7 +21,7 @@ system clock to be near correct before samples will be processed
properly. You will not be able to use it to run autonomously, nor will
it reliably recover from a trashed or zeroed system clock.
== Description ==
== Description
This driver supports the Arbiter 1088A/B Satellite Controlled Clock. The
claimed accuracy of this clock is 100 ns relative to the PPS output when
......@@ -91,7 +91,7 @@ A three-stage median filter is used to reduce jitter and provide a
dispersion measure. The driver makes no attempt to correct for the
intrinsic jitter of the radio itself.
== Monitor Data ==
== Monitor Data
When enabled by the +flag4+ option, an additional line containing
the latitude, longitude, elevation and optional deviation data is
......@@ -103,7 +103,7 @@ The deviation data consists of the mean offset and standard deviation of
the external PPS signal relative the GPS signal, both in microseconds
over the last 16 seconds.
== Driver Options ==
== Driver Options
+unit+ 'number'::
The driver unit number, defaulting to 0. Used as a distinguishing
......@@ -137,21 +137,21 @@ over the last 16 seconds.
+baud+ 'number'::
Overrides the default baud rate.
== Configuration Example ==
== Configuration Example
----------------------------------------------------------------------------
refclock arbiter
----------------------------------------------------------------------------
== Author ==
== Author
David L. Mills <mills@udel.edu>
== Additional Information ==
== Additional Information
link:refclock.html[Reference Clock Drivers]
== Known bugs ==
== Known bugs
If your Arbiter has firmware made more than 1024 weeks (19 years and 36
weeks) in the past, its internal date counter may wrap around
......
= Generic Reference Driver =
= Generic Reference Driver
include::html.include[]
== Name ==
== Name
refclock_generic - multidevice parse driver for generic time radios and GPSDOs.
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: generic
......@@ -13,7 +13,7 @@ Reference ID: DCF | DCFa | DCFp | GPS | MSF
Serial Port: /dev/refclock-'u'; TTY mode according to clock type
PPS device: /dev/refclockpps-'u'; alternate PPS device
== Warning ==
== Warning
Most modes of this driver report only two-digit years, and are thus
reliant on the system clock to be near correct before samples will be
......@@ -22,7 +22,7 @@ autonomously, nor will they reliably recover from a trashed or zeroed
system clock. The only exceptions are the Schweitzer 240x and the
Trimble TAIP/TSIP modes.
== Description ==
== Description
The generic driver supports many different clock
types/configurations by plugging type-specific packet-parsing
......@@ -57,7 +57,7 @@ controls the way time offsets are determined.
The use of the PPS option requires receivers with an accuracy of better
than 1ms.
== Timecode variables listed by {ntpqman} ==
== Timecode variables listed by {ntpqman}
The ntpq program can read and display several clock variables. These
hold the following information:
......@@ -83,7 +83,7 @@ refclock_ppsskew::
refclock_ppstime::
The PPS timestamp.
== Supported Devices ==
== Supported Devices
Twenty-five clock types are supported by the GENERIC driver
and any number of these clocks may be operational at any one time.
......@@ -311,7 +311,7 @@ See comment from subtype 20 clock.
Actual data formats and setup requirements of the various clocks can be
found in link:parsedata.html[NTP GENERIC clock data formats].
== Operation ==
== Operation
The reference clock support software carefully monitors the state
transitions of the receiver. All state changes and exceptional events
......@@ -348,7 +348,7 @@ hardware used. To select PPS support, the subtype parameter is the subtype
value as above plus 128. If 128 is not added to the subtype value, PPS will
be detected to be available but will not be used.
== Hardware PPS support ==
== Hardware PPS support
For PPS to be used, add 128 to the subtype parameter.
......@@ -359,7 +359,7 @@ information to be fed in e.g. via the parallel port (if supported by the
underlying operation system) and the date/time telegrams to be handled
via the serial port.
== Monitor Data ==
== Monitor Data
Clock state statistics are written hourly to the syslog
service. Online information can be found by examining the clock
......@@ -445,7 +445,7 @@ screen width and looks similar to:
gps_cfg[5]="[0x9] BLOCK II"
----------------------------------------
== Driver Options ==
== Driver Options
+unit+ 'number'::
The driver unit number, defaulting to 0. Used as a distinguishing
......@@ -484,11 +484,11 @@ screen width and looks similar to:
+baud+ 'number'::
Not used by this driver. Baud rate is implied by the selected mode.
== Configuration Examples ==
== Configuration Examples
See the examples above under "Supported devices"
== Making your own generic clocks ==
== Making your own generic clocks
The generic clock mechanism deviates from the way other NTP reference
clocks work. For a short description of how to build generic reference
......
= GPSD JSON client driver =
= GPSD JSON client driver
include::html.include[]
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: gpsd
Reference ID: GPSD
Serial Port: /dev/gps__u__
== Description ==
== Description
This driver is a client driver to the _GPSD_ daemon, which over time has
become increasingly popular for UN*Xish platforms. _GPSD_ can manage
......@@ -53,7 +53,7 @@ The acronym [underline]#IBT# is used here as a synonym for "in-band
time" from the data channel of the receiver, no matter what objects
were used to obtain it.
== Naming a Device ==
== Naming a Device
The _GPSD_ driver uses the same device name as the NMEA driver, namely
+/dev/gpsu+. There is a simple reason for that: While the NMEA driver
......@@ -75,7 +75,7 @@ discipline to the character special file, which is not possible when
running with root privileges already dropped. This is not likely to
change in the future.
== The \'mode' word ==
== The \'mode' word
A few operational modes can be selected with the mode word.
......@@ -117,7 +117,7 @@ use IBT alone over not getting synchronised at all.
| 2..31 2+|'(reserved for future extension, do not use)'
|===========================================================================
== Syslog flood throttle ==
== Syslog flood throttle
This driver can create a lot of syslog messages when things go wrong,
and cluttering the log files is frowned upon. So we attempt to log
......@@ -130,7 +130,7 @@ flood throttle disabled for extended periods is not recommended unless the
log files are closely monitored.
== PPS secondary clock unit ==
== PPS secondary clock unit
Units with numbers ≥128 act as secondary clock unit for the primary
clock unit (u mod 128). A secondary unit processes only the PPS data
......@@ -161,7 +161,7 @@ sample buffer at this point to avoid the use of stale PPS data.
as fudge +time1+. Only the fudge values +time1+ and the +flag1+ option
have an impact on secondary units.
== Clockstats ==
== Clockstats
If flag4 is set when the driver is polled, a clockstats record is
written for the primary clock unit. (The secondary PPS unit does not
......@@ -193,7 +193,7 @@ the last poll.
since the last poll.
|===========================================================================
== Driver Options ==
== Driver Options
+unit+ 'number'::
The driver unit number, defaulting to 0. Used as a distinguishing
......@@ -248,7 +248,7 @@ signal, it should not be used to create a possible PPS peer: These get
extra clout and can effectively become the sole source of input for the
control loop. You do not want to use sloppy data for that.
== Configuration Example ==
== Configuration Example
----------------------------------------------------------------------------
# Conentional mode 2 on unit 0, IBD only, experimental automatic mode
......@@ -259,7 +259,7 @@ server gpsd unit 0 minpoll 4 maxpoll 4 time1 0.142
server gpsd unit 128 minpoll 4 maxpoll 4 time1 0.001500
----------------------------------------------------------------------------
== Known bugs ==
== Known bugs
If your GPS has firmware made more than 1024 weeks (19 years and 36
weeks) in the past, its internal date counter may well wrap around
......
= How to Write a Reference Clock Driver =
= How to Write a Reference Clock Driver
include::html.include[]
[cols="10%,90%",frame="none",grid="none",style="verse"]
......@@ -10,11 +10,11 @@ You need a little magic.
|==============================
== Related Links ==
== Related Links
include::includes/misc.adoc[]
== Table of Contents ==
== Table of Contents
* link:#desc[Description]
* link:#file[Files Which Need to be Changed]
......@@ -23,7 +23,7 @@ include::includes/misc.adoc[]
'''''
== When Not to Write a Driver ==
== When Not to Write a Driver
If the device you are trying to support is an exotic GPS, you should
probably not write an +ntpd+ driver for it. Instead, check to see if
......@@ -43,7 +43,7 @@ allowing you support a new device type by writing only a parser for
its sentences.
[[desc]]
== Structure of a Driver ==
== Structure of a Driver
NTP reference clock support maintains the fiction that the clock is
actually an ordinary server in the NTP tradition, but operating at a
......@@ -128,7 +128,7 @@ assigned a unique long-form driver name, short-form driver name and
device name. The existing assignments are in the
link:refclock.html[Reference Clock Drivers] page and its dependencies.
== Conventions, Fudge Factors and Flags ==
== Conventions, Fudge Factors and Flags
Most drivers support manual or automatic calibration for systematic
offset bias using values encoded in the +refclock+ configuration command.
......@@ -144,7 +144,7 @@ Once the its value has stabilized, the value can be inserted in the
configuration file and the calibration feature disabled.
[[file]]
== Files Which Need to be Changed ==
== Files Which Need to be Changed
When a new reference clock driver is installed, the following files need
to be edited. Note that changes are also necessary to properly integrate
......@@ -174,7 +174,7 @@ decidedly beyond the scope of this page.
correspondence with the type number.
[[intf]]
== Interface Routine Overview ==
== Interface Routine Overview
+refclock_newpeer+ - initialize and start a reference clock.::
Allocates and initializes the interface structure which
......@@ -226,7 +226,7 @@ decidedly beyond the scope of this page.
and save it in the circular buffer (see below).
[[pps]]
== Pulse-per-Second Interface ==
== Pulse-per-Second Interface
When the Pulse-per-Second Application Interface (RFC 2783) is present, a
compact PPS interface is available to all drivers. See the
......
= Hewlett Packard GPS Receivers - HP 58503A and HP Z3801A =
= Hewlett Packard GPS Receivers - HP 58503A and HP Z3801A
include::html.include[]
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: hpgps
......@@ -9,14 +9,14 @@ Reference ID: GPS
Driver ID: GPS_HP
Serial Port: /dev/hpgps__u__; 9600bps 8N1, 19200bps 7N2 for the HP Z3801A
== Warning ==
== Warning
As of September 2017 we have reports that the internal clock on a
Z3801A was observed to roll over to 1998 (see
link:rollover.html[Rollover issues in time sources]). Users should
audit for rollover before deploying any of these devices.
== Description ==
== Description
This driver supports the HP 58503A Time and Frequency Reference Receiver
and HP Z3801A GPS Receiver. It will probably work with other Z38xx models.
......@@ -74,14 +74,14 @@ the right line parameters.
The timekeeping portion of HP's business was sold to Symmetricom; Symmetricom
was later acquired by https://www.microsemi.com/[Microsemi].
== Rollover compensation ==
== Rollover compensation
Some devices in this product line have a front-panel display of
date-time and controls to manipulate it. On these, it is possible to
reset the device's hidden base date for your current era. Consult
your documentation for details.
== Driver Options ==
== Driver Options
+unit+ 'number'::
The driver unit number, defaulting to 0. Used as a distinguishing
......@@ -115,7 +115,7 @@ your documentation for details.
+baud+ 'number'::
Overrides the default baud rate.
== Configuration Example ==
== Configuration Example
----------------------------------------------------------------------------
refclock hpgps
......
= JJY Receivers =
= JJY Receivers
include::html.include[]
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: jjy
Reference ID: JJY
Serial Port: +/dev/jjyu+; See corresponding receiver
== Warning ==
== Warning
Some modes of this driver report only two-digit years, and are thus
reliant on the system clock to be near correct before samples will be
......@@ -16,7 +16,7 @@ processed properly. You will not be able to use them to run
autonomously, nor will it reliably recover from a trashed or zeroed
system clock.
== Description ==
== Description
This driver supports the following the JJY receivers and the GPS clock
sold in Japan, and the time service through a telephone line.
......@@ -346,7 +346,7 @@ link:
ln -s /dev/ttyUSB0 /dev/jjy0
----------------------------------------------------------------
== Monitor Data ==
== Monitor Data
The driver writes sent and received data to/from the JJY receivers, GPS
clock, and the modem into the +clockstats+ file.
......@@ -369,7 +369,7 @@ filegen clockstats file clockstats type day enable
|+-X-+ | Error message
|============================================================
== Driver Options ==
== Driver Options
+unit+ 'number'::
The driver unit number, defaulting to 0. Used as a distinguishing
......@@ -403,7 +403,7 @@ filegen clockstats file clockstats type day enable
+baud+ 'number'::
Not used by this driver. The subtype implies the baud rate.
== Configuration Examples ==
== Configuration Examples
See the examples in the Description section.
......
= Undisciplined Local Clock =
= Undisciplined Local Clock
include::html.include[]
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: localclock
Reference ID: LOCL
== Description ==
== Description
Note: *We recommend against using this driver.* A much more flexible
replacement is described on the link:orphan.html[Orphan Mode] page.
......@@ -32,11 +32,11 @@ network are available. To further protect the Internet infrastructure
from accidental or malicious exposure to this driver, the driver is
disabled if another source is available and operating.
== Monitor Data ==
== Monitor Data
No +filegen clockstats+ monitor data are produced by this driver.
== Driver Options ==
== Driver Options
+unit+ 'number'::
Not used by this driver.
......@@ -73,17 +73,17 @@ No +filegen clockstats+ monitor data are produced by this driver.
+baud+ 'number'::
Not used by this driver.
== Configuration Example ==
== Configuration Example
----------------------------------------------------------------------------
refclock local
----------------------------------------------------------------------------
== Additional Information ==
== Additional Information
link:refclock.html[Reference Clock Drivers]
== Authors ==
== Authors
David L. Mills <mills@udel.edu>
......
= NIST/USNO/PTB Modem Time Services =
= NIST/USNO/PTB Modem Time Services
include::html.include[]
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: modem
......@@ -10,7 +10,7 @@ Serial Port: /dev/modem__u__; 9600 8N1
Features: tty_clk
Requires: a dial-out device.
== Warning ==
== Warning
The ACTS and USNO modes of this driver report only two-digit years, and is thus
reliant on the system clock to be near correct before samples will be
......@@ -18,7 +18,7 @@ processed properly. You will not be able to use it to run
autonomously, nor will it reliably recover from a trashed or zeroed
system clock.
== Description ==
== Description
This driver supports the US (NIST and USNO) and European (PTB (Germany),
NPL (UK), etc.) modem time services, as well as Spectracom GPS receivers
......@@ -84,7 +84,7 @@ settings are 12 (1.1 hours) for +minpoll+ and 17 (36 hours) for
+maxpoll+. Ordinarily, the poll interval will start at +minpoll+ and
ramp up to +maxpoll+ in a day or two.
== US Phone Numbers and Formats ==
== US Phone Numbers and Formats
Note: Phone numbers include the entire Hayes modem command, including
the +ATDT+ and other control codes as may be necessary. For most cases
......@@ -135,12 +135,12 @@ receiver requires a +T+ 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.
== Monitor Data ==
== Monitor Data
The received timecode is written as-is to the +clockstats+ file along
with the Hayes connection and hang-up commands and result codes.
== Driver Options ==
== Driver Options
+unit+ 'number'::
The driver unit number, defaulting to 0. Used as a distinguishing
......@@ -173,17 +173,17 @@ with the Hayes connection and hang-up commands and result codes.
+baud+ 'number'::
Overrides the default baud rate.
== Configuration Example ==
== Configuration Example
----------------------------------------------------------------------------
refclock modem
----------------------------------------------------------------------------
== Author ==
== Author
David L. Mills <mills@udel.edu>
== Additional Information ==
== Additional Information
link:refclock.html[Reference Clock Drivers]
......
= NeoClock4X - DCF77 / TDF serial line receiver + =
= NeoClock4X - DCF77 / TDF serial line receiver +
include::html.include[]
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: neoclock
......@@ -10,14 +10,14 @@ Serial Port: /dev/neoclock4x-u
image:pic/neoclock4x.gif[float="right",link="http://www.linum.com"]
== Warning ==
== Warning
This driver reports only two-digit years, and is thus reliant on the
system clock to be near correct before samples will be processed
properly. You will not be able to use it to run autonomously, nor will
it reliably recover from a trashed or zeroed system clock.
== Description ==
== Description
The refclock_neoclock4x driver supports the NeoClock4X receiver
available from http://www.linum.com[Linum Software GmbH]. The receiver
......@@ -25,7 +25,7 @@ is available as a http://www.dcf77.de[DCF77] or TDF receiver. Both
receivers have the same output string. For more information about the
NeoClock4X receiver please visit http://www.linux-funkuhr.de.
== Driver Options ==
== Driver Options
link:clockopt.html[+time1+ time]::
Specifies the time offset calibration factor with the default value of
......@@ -86,13 +86,13 @@ Default setting is 0 = don't log received data and converted utc time.
+baud+ 'number'::
Overrides the default baud rate.
== Configuration Example ==
== Configuration Example
----------------------------------------------------------------------------
refclock neoclock
----------------------------------------------------------------------------
== Author ==
== Author
Please send any comments or question to
mailto:neoclock4@linum.com[neoclock4x@linum.com].
......
= Generic NMEA GPS Receiver =
= Generic NMEA GPS Receiver
include::html.include[]
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: nmea
......@@ -10,7 +10,7 @@ Serial Port: /dev/gps__u__; 4800-115200bps, 8N1
Serial Port: /dev/gpspps__u__; for PPS
Features: +tty_clk+
== Description ==
== Description
This driver supports GPS receivers with the +$GPRMC+, +$GPGLL+,
+$GPGGA+, +$GPZDA+ and +$GPZDG+ NMEA sentences by default. Note that
......@@ -89,7 +89,7 @@ The various GPS sentences that this driver recognises look like this
|<cr><lf>|Sentence terminator.
|=============================================================================
== The \'mode' byte ==
== The \'mode' byte
Specific GPS sentences and bitrates may be selected by setting bits of the \'mode' in the refclock configuration line:
......@@ -144,7 +144,7 @@ purposes should be configured to transmit the relevant data only,
e.g. one +$GPRMC+ or +$GPZDA+ per second; this will slightly reduce
jitter by reducing variation in transmission times.
== Monitor Data ==
== Monitor Data
The last GPS sentence that is accepted or rejected is written to the
clockstats file and available with +ntpq -c clockvar+. (Logging the
......@@ -195,7 +195,7 @@ To make a specific setting, select the corresponding decimal values from
the mode byte table, add them all together and enter the resulting
decimal value into the clock configuration line.
== Setting up the Garmin GPS-25XL ==
== Setting up the Garmin GPS-25XL
Switch off all output by sending it the following string.
......@@ -216,7 +216,7 @@ switched on by sending the following string.
"$PGRMC,,,,,,,,,,,,2<cr><lf>"
-----------------------------
== Driver Options ==
== Driver Options
+unit+ 'number'::
The driver unit number, defaulting to 0. Used as a distinguishing
......@@ -254,7 +254,7 @@ switched on by sending the following string.
+baud+ 'number'::
Overrides the default baud/bps rate.
== Configuration Example ==
== Configuration Example
------------------------------------------------------------------------------
refclock nmea baud 19200 # All sentences from /dev/gps0 at 19200 bps
......@@ -265,7 +265,7 @@ link:refclock.html[Reference Clock Drivers]
'''''
== Known bugs ==
== Known bugs
If your GPS has firmware made more than 1024 weeks (19 years and 36
weeks) in the past, its internal date counter will almost certainly
......
= Motorola Oncore GPS receiver =
= Motorola Oncore GPS receiver
include::html.include[]
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: oncore
......@@ -9,7 +9,7 @@ Reference ID: GPS
Serial Port: /dev/oncore.serial._u_; 9600 bps 8N1.
PPS Port: /dev/oncore.pps._u_
== Deprecation warning ==
== Deprecation warning
This refclock is deprecated and obsolete; the entire Oncore line has
been end-of-lifed. The NTPsec maintainers plan to remove it in a
......@@ -21,7 +21,7 @@ system clock to be near correct before samples will be processed
properly. You will not be able to use it to run autonomously, nor will
it reliably recover from a trashed or zeroed system clock.
== Description ==
== Description
This driver supports most models of the
https://web.archive.org/web/19990427102123/http://www.mot.com/AECS/PNSB/products/produt.html[Motorola Oncore GPS receivers]
......@@ -53,7 +53,7 @@ The driver will use the "position hold" mode with user provided
coordinates, the receiver's built-in site-survey, or a similar algorithm
implemented in this driver to determine the antenna position.
== Monitor Data ==
== Monitor Data
The driver always puts a lot of useful information in the clockstats
file, and when run with debugging can be quite chatty on stdout. When
......@@ -68,7 +68,7 @@ manual page for information on how to use this option. For either
debugging or using the SHMEM option, an Oncore Reference Manual for the
specific receiver in use will be required.
== Driver Options ==
== Driver Options
+unit+ 'number'::
The driver unit number, defaulting to 0. Used as a distinguishing
......@@ -102,18 +102,18 @@ specific receiver in use will be required.
+baud+ 'number'::
Not used by this driver.
== Configuration Example ==
== Configuration Example
----------------------------------------------------------------------------
refclock oncore
----------------------------------------------------------------------------
== Additional Information ==
== Additional Information
The driver was initially developed on FreeBSD, and has since been tested
on Linux, SunOS and Solaris.
=== Configuration ===
=== Configuration
There is a driver specific configuration file +ntp.oncore+ (or
+ntp.oncore.+'u' or +ntp.oncore+'u' if you must distinguish between more
......@@ -131,7 +131,7 @@ the PPS signal that is `on-time' can be set with the keywords
[ASSERT/CLEAR] and the word HARDPPS will cause the PPS signal to control
the kernel PLL.
=== Performance ===
=== Performance
Even the newest of these variants, the M12+T with firmware dated 9 Jun
2004 now reports bad dates due to era rollover.
......
= PPS Clock Discipline =
= PPS Clock Discipline
include::html.include[]
== Synopsis ==
== Synopsis
["verse",subs="normal"]
Name: pps
......@@ -10,7 +10,7 @@ Driver ID: PPS
Serial or Parallel Port: /dev/pps__u__
Requires: link:kernpps.html[PPSAPI Interface for Precision Time Signals]
== Description ==
== Description
This driver furnishes an interface for the pulse-per-second (PPS) signal
produced by a cesium clock, radio clock or related devices. It can be
......@@ -87,7 +87,7 @@ In a similar scenario a PPS signal can be used to discipline the clock
between updates produced by the modem driver. This would provide precise
synchronization without needing the Internet at all.
== Driver Options ==
== Driver Options
+unit+ 'number'::
The driver unit number, defaulting to 0. Used as a distinguishing
......@@ -124,7 +124,7 @@ synchronization without needing the Internet at all.
+baud+ 'number'::
Not used by this driver.
== Configuration Example ==
== Configuration Example
----------------------------------------------------------------------------
refclock pps unit 0 flag2 1 # Capture PPS on trailing edge of pps0
......@@ -135,7 +135,7 @@ active; thus no "refclock pps" is required unless you need to set a
driver option. It is initialized by whatever other driver is using
it, which will be one of generic, nmea, or spectracom.
== Clockstats ==
== Clockstats
If clockstats is enabled, the driver will log a few counters. Examples:
......@@ -167,17 +167,17 @@ your ntpd was built in strict Classic compatibility mode it will
be a magic clock address expressing the same information in a more
opaque way.
== Additional Information ==
== Additional Information
link:refclock.html[Reference Clock Drivers]
== Reference ==
== Reference
RFC 2783::
Mogul, J., D. Mills, J. Brittenson, J. Stone and U. Windl, _Pulse-Per-Second
API for Unix-like Operating Systems, Version 1.0_, RFC 2783