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 timecodes''', were created by the TeleCommunications Working Group of the [[IRIG|Inter-Range Instrumentation Group]], 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 timecodes''', commonly known as '''IRIG timecode''', are standard formats for transferring timing information. Atomic frequency standards and [[GPS receiver]]s designed for precision timing are often equipped with an IRIG output. The standards were created by the Tele 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 200-16 from August 2016.

The different timecodes defined in the Standard have alphabetic designations. A, B, D, E, G, and H are the standards currently defined by 200-04. C was in the original specification, but was replaced by H. The main difference between codes is their rate, which varies between one pulse per minute and 10,000 pulses per second.

{|class="wikitable"

== Timecodes ==

|+IRIG time code

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 timecode

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

|-

! A

| 1000  Hz || 1 ms || 100 || 1000.1 mss || 10  Hz

|-

! B

| 100  Hz || 10 ms || 100 || 10001 mss || 1  Hz

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

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

| 2 Hz || 0.5 s || 120 || 60 s || {{frac|60}} Hz

|-

! D

| 1/{{frac|60 }} Hz || 160000 minutems || 60 || 13600 hours || 1/{{frac|3600 }} Hz

|-

! E

| 10  Hz || 100 ms || 100 || 10 s || 0.1  Hz

|-

! G

| 10 kHz10000 Hz || 0.1 ms || 100 || 100.01 mss || 100  Hz

|-

! H

| 1  Hz || 11000 sms || 60 || 160 minutes || 1/{{frac|60 }} Hz

|}

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

Other differences are:

{{efn-ua|name=CH|C<ref>{{cite 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 |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 |access-date=2011-12-23 | df = dmy-all }}</ref><ref>{{cite book | title = Handbook of Time Code Formats | url = http://www.vk7krj.com/ham_stuff_pics/Handbook_of_Time_Code_Formats.pdf | publisher = Datum Inc. | edition = Seventh | year = 1987 | page = 18 | access-date = 2024-03-18 | 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.}}

;Form Designation:

}}

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:

;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>

;[[Carrier Resolutionfrequency]]:

<ol start=0 type=1>

<li>No carrier (DCLS)</li>

<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:

<ol start=0 type=1>

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

<li>BCD ([[binary-coded decimal]] Day_of_year, hours, minutes, and (for some formats) seconds and fractions), CF (control functions), SBS (straight binary seconds_of_day)

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

<li>BCD, CF</li>

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

<li>BCD</li>

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

<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><!--

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

</ol>

--><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"

|+ Permissible Code Formats

! Format

! Modulation FrequencyType

! Carrier Frequency / Resolution

! Coded Expressions

|-

! A

| 0,1,2

| 0,3,4,5

| 0,1,2,3,4,5,6,7

|-

! B

| 0,1,2

| 0,2,3,4,5

| 0,1,2,3,4,5,6,7

|-

! D

| 0,1

| 0,1,2

| 1,2

|-

! E

| 0,1

| 0,1,2

| 1,2,5,6

|-

! G

| 0,1,2

| 0,4,5

| 1,2,5,6

|-

! H

| 0,1

| 0,1,2

| 1,2

|}

Thus the complete signal identification number consists of one letter and three digits. E.g.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.

1 kHz carrier/1 ms resolution, 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 year (0-99), the day of the year (1-3661–366), hours, minutes, and seconds. Year Informationnumbers asare tonot whichincluded, centuryso itthe is,timecode isrepeats not transmittedannually. [[Leap second]] announcements are not provided. Although information is transmitted only once per second, a device can sychronizesynchronize 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 or(carrier reducedattenuated at least 3×, inDC amplitudesignal 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 113 ⟶ 131:

Bit 0 is the frame marker bit P_r. Every 10th bit starting with bit 9, 19, 29, ... 99 is also a marker bit, known as position identifiers P₁, P₂, ..., P₉, P₀. Thus, two marker bits in a row (P₀ followed by P_r) marks the beginning of a frame. The frame encodes the time of the leading edge of the frame marker bit.

All other bits are data bits, which are transmitted as binary 0 if they have no other assigned purpose.

Generally, groups of 4 bits are used to encode BCD digits. Bits are assigned little-endian within fields.

Line 119 ⟶ 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 130 ⟶ 148:

No parity or check bits are included. Error detection can be achieved by comparing consecutive frames to see if they encode consecutive timestamps.

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.

==References IRIG timecode ==

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

*[https://wsmrc2vger.wsmr.army.mil/rcc/manuals/200-04/TT-45.pdf IRIG standard 200-04 (PDF)]

|+ IRIG A time code structure

! Bit || Weight || Meaning

|rowspan=21|

! Bit || Weight || Meaning

|rowspan=21|

! Bit || Weight || Meaning

|rowspan=21|

! Bit || Weight || Meaning

|rowspan=21|

! Bit || Weight || Meaning

|-

|bgcolor=lightpink| 00 ||bgcolor=lightpink| P_r ||bgcolor=lightpink| Frame marker

| 20 || 1 ||rowspan=7| Hours<br/>(0–23)

| 40 || 100 ||rowspan=2| Day of year<br/>(1–366)

|bgcolor=lightgrey| 60 ||bgcolor=lightgrey| 0 ||rowspan=9 bgcolor=lightgrey| Unused,<br/>available for<br/>Control<br/>Functions

| 80 || 1 ||rowspan=18| Straight<br/>Binary<br />Seconds<br/>(0–86399)

|-

| 01 || 1 ||rowspan=8| Seconds<br/> (00–59)

| 21 || 2

| 41 || 200

|bgcolor=lightgrey| 61 ||bgcolor=lightgrey| 0

| 81 || 2

|-

| 02 || 2

| 22 || 4

|bgcolor=lightgrey| 42 ||bgcolor=lightgrey| 0 ||rowspan=3 bgcolor=lightgrey| Unused

|bgcolor=lightgrey| 62 ||bgcolor=lightgrey| 0

| 82 || 4

|-

| 03 || 4

| 23 || 8

|bgcolor=lightgrey| 43 ||bgcolor=lightgrey| 0

|bgcolor=lightgrey| 63 ||bgcolor=lightgrey| 0

| 83 || 8

|-

| 04 || 8

|bgcolor=lightgrey| 24 ||bgcolor=lightgrey| 0

|bgcolor=lightgrey| 44 ||bgcolor=lightgrey| 0

|bgcolor=lightgrey| 64 ||bgcolor=lightgrey| 0

| 84 || 16

|-

|bgcolor=lightgrey| 05 ||bgcolor=lightgrey| 0

| 25 || 10

| 45 || 0.1 ||rowspan=4|Tenths of seconds<br/>(0.0–0.9)

|bgcolor=lightgrey| 65 ||bgcolor=lightgrey| 0

| 85 || 32

|-

| 06 || 10

| 26 || 20

| 46 || 0.2

|bgcolor=lightgrey| 66 ||bgcolor=lightgrey| 0

| 86 || 64

|-

| 07 || 20

|bgcolor=lightgrey| 27 ||bgcolor=lightgrey| 0 ||rowspan=2 bgcolor=lightgrey| Unused

| 47 || 0.4

|bgcolor=lightgrey| 67 ||bgcolor=lightgrey| 0

| 87 || 128

|-

| 08 || 40

|bgcolor=lightgrey| 28 ||bgcolor=lightgrey| 0

| 48 || 0.8

|bgcolor=lightgrey| 68 ||bgcolor=lightgrey| 0

| 88 || 256

|- bgcolor=lightpink

| 09 || P₁ || Position identifier

| 29 || P₃ || Position identifier

| 49 || P₅ || Position identifier

| 69 || P₇ || Position identifier

| 89 || P₉

|-

| 10 || 1 ||rowspan=8| Minutes<br/>(00–59)

| 30 || 1 ||rowspan=9| Day of year<br/>(1–366)

| 50 || 1 ||rowspan=9| Year<br/>(00–99)

|bgcolor=lightgrey| 70 ||bgcolor=lightgrey| 0 ||rowspan=9 bgcolor=lightgrey| Unused,<br/>available for<br/>Control<br/>Functions

| 90 || 512

|-

| 11 || 2

| 31 || 2

| 51 || 2

|bgcolor=lightgrey| 71 ||bgcolor=lightgrey| 0

| 91 || 1024

|-

| 12 || 4

| 32 || 4

| 52 || 4

|bgcolor=lightgrey| 72 ||bgcolor=lightgrey| 0

| 92 || 2048

|-

| 13 || 8

| 33 || 8

| 53 || 8

|bgcolor=lightgrey| 73 ||bgcolor=lightgrey| 0

| 93 || 4096

|-

|bgcolor=lightgrey| 14 ||bgcolor=lightgrey| 0

|bgcolor=lightgrey| 34 ||bgcolor=lightgrey| 0

|bgcolor=lightgrey| 54 ||bgcolor=lightgrey| 0

|bgcolor=lightgrey| 74 ||bgcolor=lightgrey| 0

| 94 || 8192

|-

| 15 || 10

| 35 || 10

| 55 || 10

|bgcolor=lightgrey| 75 ||bgcolor=lightgrey| 0

| 95 || 16384

|-

| 16 || 20

| 36 || 20

| 56 || 20

|bgcolor=lightgrey| 76 ||bgcolor=lightgrey| 0

| 96 || 32768

|-

| 17 || 40

| 37 || 40

| 57 || 40

|bgcolor=lightgrey| 77 ||bgcolor=lightgrey| 0

| 97 || 65536

|-

|bgcolor=lightgrey| 18 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| Unused

| 38 || 80

| 58 || 80

|bgcolor=lightgrey| 78 ||bgcolor=lightgrey| 0

|bgcolor=lightgrey| 98 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| Unused

|- bgcolor=lightpink

| 19 || P₂ || Position identifier

| 39 || P₄ || Position identifier

| 59 || P₆ || Position identifier

| 79 || P₈ || Position identifier

| 99 || P₀ || Position identifier

|}

{{Clear}}

==ExternalIRIG linksJ timecode==

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

* [http://irigb.com IRIGB.com]: site dedicated to irigb with standard and figures.

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

* [http://www.microsystemes.com/Time_uk.html IRIG B equipment]

* 1 start bit

* [http://ionetrics.com/hardware_annotator_cl.htm IRIG B Time Generator]

* 7 data bits

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

* 1 [[odd parity]] bit

* 1 stop bit

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

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

[[Category:Timecodes]]

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

[[de:IRIG Timecode]]

* SOH is the ASCII "start of header" code, with binary value <code>0x01</code>.

* DDD is the [[ordinal date]] (day of year), from 1 to 366.

* HH, MM and SS are the time of the start bit.

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

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

IRIG J-2 timecode 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>

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

The full-timecode 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

|-

|}

== See also ==

* [[Precision Time Protocol]]

* [[Network Time Protocol]]

* [[SMPTE timecode]]

== References ==

{{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=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 |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

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

[[Category:1960 introductions]]

[[Category:Timecodes]]