IRIG timecode: Difference between revisions

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{{Short description|Standard formats for transferring time information}}

'''Inter-range instrumentation group time codes''', commonly known as '''IRIG time codes''', are standard formats for transferring timing information. Atomic frequency standards and GPS receivers designed for precision timing are often equipped with an IRIG output. The standards were created by the TeleCommunications Working Group of the U.S. military's [[Inter-Range Instrumentation Group]] (IRIG), the standards body of the [[Range Commanders Council]]. Work on these standards started in October 1956, and the original standards were accepted in 1960.

'''Inter-range instrumentation group time codestimecodes''', commonly known as '''IRIG time codestimecode''', are standard formats for transferring timing information. Atomic frequency standards and [[GPS receiversreceiver]]s designed for precision timing are often equipped with an IRIG output. The standards were created by the TeleCommunicationsTele Communications Working Group of the U.S. military's [[Inter-Range Instrumentation Group]] (IRIG), the standards body of the [[Range Commanders Council]]. Work on these standards started in October 1956, and the original standards were accepted in 1960.

The original formats were described in IRIG Document 104-60, later revised and reissued in August 1970 as IRIG Document 104-70, upgraded later that year as the IRIG Document to the status of a Standard, IRIG Standard 200-70. The latest version of the Standard is IRIG Standard 200-04.

The original formats were described in IRIG Document 104-60, later revised and reissued in August 1970 as IRIG Document 104-70, upgraded later that year as the IRIG Document to the status of a Standard, IRIG Standard 200-70. The latest version of the Standard is IRIG Standard 200-0416 from August 2016.

== Time codes ==

The different timecodes defined in the Standard have alphabetic designations. A, B, D, E, G, and H are the standards currently defined by IRIG Standard 200-04.

== Timecodes ==

C<ref>{{Citation |url=http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA000295 |format=pdf |title=Special Hardware for ARL Analysis of ACODAC Data |type=technical report |first1=Richard O. |last1=Grohman |first2=Larry L. |last2=Mellenbruch |first3=Felix J. |last3=Sowic |date=1974-03-14 |publisher=Texas University at Austin |id=ARL-TM-74-12 |accessdate=2011-12-23}}</ref><ref>{{Citation |title=Handbook of Time Code Formats |url=http://www.vk7krj.com/ham_stuff_pics/Handbook_of_Time_Code_Formats.pdf |author=Datum Inc. |year=1987 |page=18 |accessdate=2013-06-24}}</ref> was in the original specification, but was replaced by H.

The different timecodes defined in the Standard have alphabetic designations. A, B, D, E, G, and H are the standards currently defined by IRIG Standard 200-04.

The main difference between codes is their rate, which varies between one pulse per minute and 10,000 pulses per second.

{|class="wikitable sortable"

|+IRIG time codetimecode

! Code || Bit rate || Bit time || Bits per frame || Frame time || Frame rate

|-

! A

| 1000&nbsp;Hz || 1 ms || 100 || 1000.1 mss || 10&nbsp;Hz

|-

! B

| 100&nbsp;Hz || 10 ms || 100 || 10001 mss || 1&nbsp;Hz

|- style="text-decoration:line-through"

! C{{efn-ua|name=CH}}

! C

| 2&nbsp;Hz || 0.5 s || 120 || 160 minutes || {{frac|60}}&nbsp;Hz

|-

! D

| {{frac|60}}&nbsp;Hz || 160000 minutems || 60 || 13600 hours || {{frac|3600}}&nbsp;Hz

|-

! E

Line 30:

|-

! G

| 1010000&nbsp;kHzHz || 0.1 ms || 100 || 100.01 mss || 100&nbsp;Hz

|-

! H

| 1&nbsp;Hz || 11000 sms || 60 || 160 minutes || {{frac|60}}&nbsp;Hz

|}

{{notelist-ua|name=CH|refs=

{{efn-ua|name=CH|C<ref>{{Citationcite tech report |url=https://apps.dtic.mil/sti/pdfs/ADA000295.pdf |archive-url=https://web.archive.org/web/20130408112407/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA000295 |url-status=live |archive-date=April 8, 2013 |format=pdf |title=Special Hardware for ARL Analysis of ACODAC Data |type=technical report |first1=Richard O. |last1=Grohman |first2=Larry L. |last2=Mellenbruch |first3=Felix J. |last3=Sowic |date=1974-03-14 |publisher=Texas University at Austin |id=ARL-TM-74-12 |accessdateaccess-date=2011-12-23 | df = dmy-all }}</ref><ref>{{Citationcite book | title = Handbook of Time Code Formats | url = http://www.vk7krj.com/ham_stuff_pics/Handbook_of_Time_Code_Formats.pdf |author publisher = Datum Inc. | edition = Seventh | year = 1987 | page = 18 |accessdate access-date =2013 2024-0603-2418 | archive-url = https://web.archive.org/web/20230308040915/https://www.vk7krj.com/ham_stuff_pics/Handbook_of_Time_Code_Formats.pdf | archive-date = 2023-03-08 | url-status = live | via = vk7krj.com | df = dmy-all}}</ref> was in the original specification, but was replaced by H.}}

}}

The bits are modulated on a carrier. A three-digit suffix specifies the type and frequency of the carrier, and which optional information is included:

Line 40 ⟶ 44:

;Modulation type:

<ol start=0 type=1>

<li>(DCLS) [[Direct Currentcurrent|DC]] Levellevel Shiftshift (DCLS) ([[Pulse-width modulation|pulse width coded]] without carrier)</li>

<li>Sine wave carrier ([[amplitude modulated]])</li>

<li>[[Manchester code|Manchester]] modulated</li>

</ol>

Line 50 ⟶ 54:

<li>100&nbsp;Hz (10 ms resolution)</li>

<li>1&nbsp;kHz (1 ms resolution)</li>

<li>10&nbsp;kHz (100 µsμs resolution)</li>

<li>100&nbsp;kHz (10 µsμs resolution)</li>

<li>1&nbsp;MHz (1 µsμs resolution)</li>

</ol>

;Coded expressions:

:[[Binary-coded decimal|Binary-coded decimal (BCD)]] day of year, hours, minutes, and (for some formats) seconds and fractions are always included. Optional components are:

:* Year number (00–99; century is not coded)

:* User-defined "control functions (CF)" occupying bits not defined by IRIG

:* "Straight binary seconds (SBS)", a 17-bit binary counter that counts from 0 to 86399.

:The types are:<ol start=0 type=1><!--

--><li>BCD, CF, SBS</li><!--

--><li>BCD, CF</li><!--

--><li>BCD</li><!--

--><li>BCD, SBS</li><!--

--><li>BCD, BCD_Year, CF, SBS</li><!--

--><li>BCD, BCD_Year, CF</li><!--

--><li>BCD, BCD_Year</li><!--

--><li>BCD, BCD_Year, SBS</li><!--

--></ol>

The recognized signal identification numbers for each format according to the standard 200-04 consist of:

{| class="wikitable" border="1"

Line 111 ⟶ 116:

Thus the complete signal identification number consists of one letter and three digits. For example, the signal designated as B122 is deciphered as follows: Format B, Sine wave (amplitude modulated), 1&nbsp;kHz carrier, and Coded expressions BCDTOY.

The most commonly used of the standards is IRIG B, then IRIG A, then probably IRIG G. Time codeTimecode formats directly derived from IRIG H are used by [[National Institute of Standards and Technology|NIST]] [[radio station]]s [[WWV (radio station)|WWV]], [[WWVH]] and [[WWVB]].

For example, one of the most common formats, IRIG B122:

:IRIG B122 transmits one hundred pulses per second on an amplitude modulated 1&nbsp;kHz sine wave carrier, encoding information in BCD. This means that 100 bits of information are transmitted every second. The time frame for the IRIG B standard is 1 second, meaning that one data frame of time information is transmitted every second. This data frame contains information about the day of the year (1–366), hours, minutes, and seconds. Year numbers are not included, so the time codetimecode repeats annually. [[Leap second]] announcements are not provided. Although information is transmitted only once per second, a device can synchronize its time very accurately with the transmitting device by using a [[phase-locked loop]] to synchronize to the carrier. Typical commercial devices will synchronize to within 1 microsecond using IRIG B timecodes.

== Time codeTimecode structure ==

IRIG time codetimecode is made up of repeating frames, each containing 60 or 100 bits. The bits are numbered from 0 through 59 or 99.

At the start of each bit time, the IRIG time codetimecode enables a signal (sends a carrier, raises the DC signal level, or transmits Manchester 1 bits). The signal is disabled (carrier attenuated at least 3×, DC signal level lowered, or Manchester 0 bits transmitted), at one of three times during the bit interval:

* After 0.2 of a bit time, to encode a binary 0

* After 0.5 of a bit time, to encode a binary 1

Line 132 ⟶ 137:

* Bits 10–13 encode minutes, and bits 15–17 encode tens of minutes (0–59)

* Bits 20–23 encode hours, and bits 25–26 encode tens of hours (0–23)

* Bits 30-33 encode [[Ordinal date|day of year]], 35-38 encode tens of days, and bits 40–41 encode hundreds of days (1–366)

* Bits 45–48 encode tenths of seconds (0–9)

* Bits 50–53 encode years, and bits 55–58 encode tens of years (0–99)

Line 145 ⟶ 150:

Unassigned 9-bit fields between consecutive marker bits are available for user-defined "control functions". For example, the [[IEEE 1344]] standard defines functions for bits 60–75.

== IRIG Time Codetimecode ==

{|class=wikitable style="text-align:center;"

|+ IRIG A time code structure

Line 280 ⟶ 285:

{{Clear}}

==IRIG J time codetimecode==

IRIG standard 212-00 defines a different time-code, based on [[RS-232]]-style [[asynchronous serial communication]].

The time codetimecode consists of [[ASCII]] characters, each transmitted as 10 bits:

* 1 start bit

* 7 data bits

Line 289 ⟶ 294:

The on-time marker is the leading edge of the first start bit.

IRIG J-1 time codetimecode consists of 15 characters (150 bit times), sent once per second at a baud rate of 300 or greater:

<nowiki><SOH>DDD:HH:MM:SS<CR><LF></nowiki>

Line 298 ⟶ 303:

* The code is terminated by a [[Newline|CR+LF]] pair.

At the end of the time codetimecode, the serial line is idle until the start of the next code. There is no idle time between other characters.

IRIG J-2 time codetimecode consists of 17 characters (170 bit times), sent 10 times per second at a baud rate of 2400 or greater:

<nowiki><SOH>DDD:HH:MM:SS.S<CR><LF></nowiki>

Line 306 ⟶ 311:

This is the same, except that tenths of seconds are included.

The full-time codetimecode specification is of the form "IRIG J-''xy''", where ''x'' denotes the variant, and ''y'' denotes a baud rate of 75×2^''y''.

Normally used combinations are J-12 through J-14 (300, 600, and 1200 baud), and J-25 through J-29 (2400 through 38400 baud).

{| class="wikitable"

|-

! Combination J-''xy'' !! variant (''x'') !! ''y'' !! 2^''y'' !! Baud = 75 × 2^''y''

|-

| J-12|| 1|| 2|| 4|| 300

|-

| J-13|| 1|| 3|| 8|| 600

|-

| J-14|| 1|| 4|| 16|| 1200

|-

|colspan=5|

|-

| J-25|| 2|| 5|| 32|| 2400

|-

| J-26|| 2|| 6|| 64|| 4800

|-

| J-27|| 2|| 7|| 128|| 9600

|-

| J-28|| 2|| 8 || 256|| 19200

|-

| J-29|| 2|| 9|| 512|| 38400

|-

|}

== TimeSee codesalso ==

* [[Precision Time Protocol]]

* [[Network Time Protocol]]

* [[SMPTE timecode]]

== References ==

* {{Citation |last=Telecommunications and Timing Group |publisher=Range Commanders Council |___location=U.S. Army White Sands Missile Range, New Mexico |url=http://irigb.com/pdf/wp-irig-200-04.pdf |format=PDF |id=IRIG standard 200-04 |title=IRIG Serial Time Code Formats |date=September 2004 }}

* {{Citation |last=Telecommunications and Timing Group |publisher=Range Commanders Council |___location=U.S. Army White Sands Missile Range, New Mexico |url=https://wsmrc2vger.wsmr.army.mil/rcc/manuals/212-00/index.htm |format=DOC |id=IRIG standard 212-00 |title=IRIG J Asynchronous ASCII Time Code Formats |date=November 2000}}

{{reflist}}

== Sources ==

* {{Citation |last=Telecommunications and Timing Group |publisher=Range Commanders Council |___location=U.S. Army White Sands Missile Range, New Mexico |url=http://www.wsmr.army.mil/RCCsite/Documents/200-16_IRIG_Serial_Time_Code_Formats/200-16_IRIG_Serial_Time_Code_Formats.pdf |format=PDF |id=IRIG standard 200-16 |title=IRIG Serial Time Code Formats |date=August 2016 |access-date=2024-05-27 |archive-date=2018-08-26 |archive-url=https://web.archive.org/web/20180826214654/http://www.wsmr.army.mil/RCCsite/Documents/200-16_IRIG_Serial_Time_Code_Formats/200-16_IRIG_Serial_Time_Code_Formats.pdf |url-status=bot: unknown }}

* {{Citation |last=Telecommunications and Timing Group |publisher=Range Commanders Council |___location=U.S. Army White Sands Missile Range, New Mexico |url=httphttps://irigbwsmrc2vger.comwsmr.army.mil/pdfrcc/wp-irig-200manuals/212-0400/index.pdfhtm |format=PDFDOC |id=IRIG standard 200212-0400 |title=IRIG SerialJ Asynchronous ASCII Time Code Formats |date=SeptemberNovember 20042000 |access-date=2011-10-01 |archive-url=https://web.archive.org/web/20130217171957/https://wsmrc2vger.wsmr.army.mil/rcc/manuals/212-00/index.htm |archive-date=2013-02-17 |url-status=dead }}

== External links ==

* [http://www.meinberg.de/english/info/irig.htm IRIG information]&nbsp;— IRIG information page with diagrams

*[url {{Citation |title=http://www.irigb.comThe [www.irigb.com]]—IRIGB standard site - The site dedicated to IRIGB standard Time code|url=http://irigb.com }}

* {{Citation |title=The IRIGB standard site|url=http://irigb.com}}

[[Category:1960 introductions]]

[[Category:Timecodes]]