Inter-range instrumentation group time codes
Encyclopedia
Inter-range instrumentation group time codes, commonly known as IRIG timecodes, were created by the TeleCommunications Working Group of the 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.
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 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 second and 10,000 pulses per second.
Other differences are:
Form Designation:
Carrier Resolution:
Coded expressions:
The recognized signal identification numbers for each format according to the standard 200-04 consist of:
Thus the complete signal identification number consists of one letter and three digits. E.g. the signal designated as B122 is deciphered as follows: Format B, Sine wave (amplitude modulated),
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 code formats directly derived from IRIG H are used by NIST
radio station
s 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 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 (1–366), hours, minutes, and seconds. Information as to which century it is, is not transmitted. Leap second
announcements are not provided. Although information is transmitted only once per second, a device can sychronize its time very accurately with the transmitting device by using a phase locked loop. Typical commercial devices will synchronize to within 1 microsecond using IRIG B timecodes.
At the start of each bit time, the IRIG time code 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:
Bit 0 is the frame marker bit Pr. 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 Pr) 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.
In IRIG G, bits 50–53 encode hundredths of seconds, and the years are encoded in bits 60–68.
Not all formats include all fields. Obviously those formats with 60-bit frames omit the straight binary seconds fields, and digits representing divisions less than one frame time (everything below hours, in the case of IRIG D) are always transmitted as 0.
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.
-style asynchronous serial communication.
The time code consists of ASCII
characters, each transmitted as 10 bits:
The on-time marker is the leading edge of the first start bit.
IRIG J-1 time code consists of 15 characters (150 bit times), sent once per second at a baud rate of 300 or greater:
DDD:HH:MM:SS
At the end of the time code, the serial line is idle until the start of the next code. There is no idle time between other characters.
IRIG J-2 time code consists of 17 characters (170 bit times), send 10 times per second at a baud rate of 2400 or greater:
DDD:HH:MM:SS.S
This is the same, except that tenths of seconds are included.
The full time code specification is of the form "IRIG J-xy", where x denotes the variant, and y denotes a baud rate of 75×2y.
Normally used combinations are J-12 through J-14 (300, 600, and 1200 baud), and J-25 through J-29 (2400 through 38400 baud).
IRIG
The Inter Range Instrumentation Group is the standards body of the Range Commanders Council . They publish a number of standards through the RCC Secretariat at White Sands Missile Range ....
, 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 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 second and 10,000 pulses per second.
| Code | Bit rate | Bit time | Bits per frame | Frame time | Frame rate |
|---|---|---|---|---|---|
| A | 1000 Hz | 1 ms | 100 | 100 ms | 10 Hz |
| B | 100 Hz | 10 ms | 100 | 1000 ms | 1 Hz |
| D | 1/60 Hz | 1 minute | 60 | 1 hour | 1/3600 Hz |
| E | 10 Hz | 100 ms | 100 | 10 s | 0.1 Hz |
| G | 10 kHz | 0.1 ms | 100 | 10 ms | 100 Hz |
| H | 1 Hz | 1 s | 60 | 1 minute | 1/60 Hz |
Other differences are:
Form Designation:
- (DCLS) Direct Current Level Shift (width coded)
- Sine wave carrier (amplitude modulated)
- ManchesterManchester codeIn telecommunication and data storage, Manchester code is a line code in which the encoding of each data bit has at least one transition and occupies the same time...
modulated
Carrier Resolution:
- No carrier (DCLS)
- 100 Hz (10 ms resolution)
- 1 kHz (1 ms resolution)
- 10 kHz (100 µs resolution)
- 100 kHz (10 µs resolution)
- 1 MHz (1 µs resolution)
Coded expressions:
- BCD (binary-coded decimalBinary-coded decimalIn computing and electronic systems, binary-coded decimal is a digital encoding method for numbers using decimal notation, with each decimal digit represented by its own binary sequence. In BCD, a numeral is usually represented by four bits which, in general, represent the decimal range 0 through 9...
Day_of_year, hours, minutes, and (for some formats) seconds and fractions), CF (control functions), SBS (straight binary seconds_of_day)
- BCD, CF
- BCD
- BCD, SBS
- BCD, BCD_Year, CF, SBS
- BCD, BCD_Year, CF
- BCD, BCD_Year
- BCD, BCD_Year, SBS
The recognized signal identification numbers for each format according to the standard 200-04 consist of:
| Format | Modulation Frequency | 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. the signal designated as B122 is deciphered as follows: Format B, Sine wave (amplitude modulated),
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 code formats directly derived from IRIG H are used by NIST
National Institute of Standards and Technology
The National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory, otherwise known as a National Metrological Institute , which is a non-regulatory agency of the United States Department of Commerce...
radio station
Radio station
Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...
s WWV, WWVH
WWVH
WWVH is the callsign of the U.S. National Institute of Standards and Technology's shortwave radio time signal station in Kekaha, on the island of Kauai in the state of Hawaii....
and WWVB
WWVB
WWVB is a NIST time signal radio station near Fort Collins, Colorado, co-located with WWV. WWVB is the station that radio-controlled clocks in most of North America use to synchronize themselves. The signal transmitted from WWVB is a continuous 60 kHz carrier wave, derived from a set of atomic...
.
For example, one of the most common formats, IRIG B122:
IRIG B122 transmits one hundred pulses per second on an amplitude modulated 1 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 (1–366), hours, minutes, and seconds. Information as to which century it is, is not transmitted. Leap second
Leap second
A leap second is a positive or negative one-second adjustment to the Coordinated Universal Time time scale that keeps it close to mean solar time. UTC, which is used as the basis for official time-of-day radio broadcasts for civil time, is maintained using extremely precise atomic clocks...
announcements are not provided. Although information is transmitted only once per second, a device can sychronize its time very accurately with the transmitting device by using a phase locked loop. Typical commercial devices will synchronize to within 1 microsecond using IRIG B timecodes.
Time code structure
IRIG time code 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 code 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
- After 0.8 of a bit time, to encode a marker bit
Bit 0 is the frame marker bit Pr. 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 Pr) 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.
- Bits 1–4 encode seconds, and bits 6–8 encode tens of seconds (0–59)
- 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 day of yearOrdinal dateAn ordinal date is a calendar date typically consisting of a year and a day of year ranging between 1 and 366 , though year may sometimes be omitted...
, 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)
- Bits 80–88 and 90–97 encode "straight binary seconds" since 00:00 on the current day (0–86399, not BCD)
In IRIG G, bits 50–53 encode hundredths of seconds, and the years are encoded in bits 60–68.
Not all formats include all fields. Obviously those formats with 60-bit frames omit the straight binary seconds fields, and digits representing divisions less than one frame time (everything below hours, in the case of IRIG D) are always transmitted as 0.
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
IEEE 1344
IEEE 1344 is a standard that defines parameters for synchrophasors for power systems. The standard added extension to the IRIG-B time code to cover year, time quality, daylight savings time, local time offset and leap second information...
standard defines functions for bits 60–75.
IRIG Time Code
| Bit | Weight | Meaning | Bit | Weight | Meaning | Bit | Weight | Meaning | Bit | Weight | Meaning | Bit | Weight | Meaning |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 00 | Pr | Frame marker | 20 | 1 | Hours (0–23) |
40 | 100 | Day of year (1–366) |
60 | 0 | Unused | 80 | 1 | Straight BinarySeconds (0–86399) |
| 01 | 1 | Seconds (00–59) |
21 | 2 | 41 | 200 | 61 | 0 | 81 | 2 | ||||
| 02 | 2 | 22 | 4 | 42 | 0 | Unused | 62 | 0 | 82 | 4 | ||||
| 03 | 4 | 23 | 8 | 43 | 0 | 63 | 0 | 83 | 8 | |||||
| 04 | 8 | 24 | 0 | 44 | 0 | 64 | 0 | 84 | 16 | |||||
| 05 | 0 | 25 | 10 | 45 | 0.1 | Tenths of seconds (0.0–0.9) |
65 | 0 | 85 | 32 | ||||
| 06 | 10 | 26 | 20 | 46 | 0.2 | 66 | 0 | 86 | 64 | |||||
| 07 | 20 | 27 | 0 | Unused | 47 | 0.4 | 67 | 0 | 87 | 128 | ||||
| 08 | 40 | 28 | 0 | 48 | 0.8 | 68 | 0 | 88 | 256 | |||||
| 09 | P1 | Position identifier | 29 | P3 | Position identifier | 49 | P5 | Position identifier | 69 | P7 | Position identifier | 89 | P9 | |
| 10 | 1 | Minutes (00–59) |
30 | 1 | Day of year (1–366) |
50 | 1 | Year (00–99) |
70 | 0 | Unused | 90 | 512 | |
| 11 | 2 | 31 | 2 | 51 | 2 | 71 | 0 | 91 | 1024 | |||||
| 12 | 4 | 32 | 4 | 52 | 4 | 72 | 0 | 92 | 2048 | |||||
| 13 | 8 | 33 | 8 | 53 | 8 | 73 | 0 | 93 | 4096 | |||||
| 14 | 0 | 34 | 0 | 54 | 0 | 74 | 0 | 94 | 8192 | |||||
| 15 | 10 | 35 | 10 | 55 | 10 | 75 | 0 | 95 | 16384 | |||||
| 16 | 20 | 36 | 20 | 56 | 20 | 76 | 0 | 96 | 32768 | |||||
| 17 | 40 | 37 | 40 | 57 | 40 | 77 | 0 | 97 | 65536 | |||||
| 18 | 0 | Unused | 38 | 80 | 58 | 80 | 78 | 0 | 98 | 0 | Unused | |||
| 19 | P2 | Position identifier | 39 | P4 | Position identifier | 59 | P6 | Position identifier | 79 | P8 | Position identifier | 99 | P0 | Position identifier |
IRIG J time code
IRIG standard 212-00 defines a different time-code, based on RS-232RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
-style asynchronous serial communication.
The time code consists of ASCII
ASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
characters, each transmitted as 10 bits:
- 1 start bit
- 7 data bits
- 1 odd parity bit
- 1 stop bit
The on-time marker is the leading edge of the first start bit.
IRIG J-1 time code consists of 15 characters (150 bit times), sent once per second at a baud rate of 300 or greater:
- SOH is the ASCII "start of header" code, with binary value
0x01. - DDD is the day of year, from 1 to 365 (or 366 in leap yearLeap yearA leap year is a year containing one extra day in order to keep the calendar year synchronized with the astronomical or seasonal year...
s). - HH, MM and SS are the time of the start bit.
- The code is terminated by a CRLF pair.
At the end of the time code, the serial line is idle until the start of the next code. There is no idle time between other characters.
IRIG J-2 time code consists of 17 characters (170 bit times), send 10 times per second at a baud rate of 2400 or greater:
This is the same, except that tenths of seconds are included.
The full time code specification is of the form "IRIG J-xy", where x denotes the variant, and y denotes a baud rate of 75×2y.
Normally used combinations are J-12 through J-14 (300, 600, and 1200 baud), and J-25 through J-29 (2400 through 38400 baud).
External links
- IRIG information IRIG information page with diagrams.
- informations on IRIGB standard "the" IRIGB standard website.