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TN-102
Sep-2009

TECHNICAL NOTE

Overview of IRIG-B Time Code Standard
Introduction
The IRIG time codes were originally developed by the Inter-Range Instrumentation Group (IRIG), part of the Range Commanders Council (RCC) of the US Army. The standard was first published in 1960 and has been revised several times by the Telecommunications and Timing Group (TTG) of the RCC. The latestversion is IRIG standard 200-04, “IRIG Serial Time Code Formats,” updated in September, 2004.

Summary
The IRIG-B time protocol is widely used by electric utilities, industrials, and others to ensure precise time synchronization of power system devices, such as breakers, relays and meters. This document describes the protocol, gives examples of how IRIG-B is used by Cyber Sciences products, andprovides references for further study.

Available Formats
Although the “IRIG-B” time code is best known, the standard actually defines a family of rate-scaled serial time codes. The six code formats use different pulse rates, or bit rates, as shown in the table below. IRIG Time Code Formats
Format IRIG-A IRIG-B IRIG-D IRIG-E IRIG-G IRIG-H Pulse Rate (or Bit Rate) 1000 PPS (pulse per second) 100 PPS1 PPM 10 PPS 10000 PPS 1 PPS Index Count Interval 1 ms 10 ms 1 minute 100 ms 0.1 ms 1 second

IRIG STANDARD 200-04

Time Code Attributes
All IRIG time code formats use pulse-width coding. A “binary 1” pulse has a duration of 50% of the index count interval, and a “binary 0” pulse has a duration of 20% of the index count interval. In addition “Position Identifiers” have a duration of 80% andare used as reference markers. IRIG time code signals may be: IRIG STANDARD 200-04 ● Unmodulated (DC level shift, no carrier signal) ● Modulated (amplitude-modulated, sine wave carrier). ● Modified Manchester (amplitude-modulated, square wave carrier). Three types of coded expressions are used in the IRIG standard: ● Binary Coded Decimal time-of-year (BCDTOY) and year (BCDYEAR) ● Control Functions(CF), set of bits reserved for user applications TIME CODE FORMATS time-of-day (0 to 86400 seconds) ● Straight Binary Seconds (SBS)

TELECOMMUNICATIONS AND TIMING GROUP

IRIG SERIAL

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TN-102 |

Sep-2009

TECH NOTE — Overview of IRIG-B Time Code Standard

IRIG STANDARD 200-04 (Continued)

IRIG Time Code Designations
In addition to the letter used to designate one of the six IRIG code formats, signal identification numbers are used to further describe specific characteristics. Thus, the complete IRIG time code designation consists of a letter and three digits, asshown below.

Format (A, B, D, E, G or H) Modulation Carrier Frequency / Resolution Coded Expressions

B006
IRIG time codes – naming convention

IRIG Signal Identification Numbers (3 Digits)
1st Digit 0 1 2 2nd Digit 0 1 2 3 4 3rd Digit 0 1 2 3 4 5 6 7 Modulation Unmodulated – DC Level Shift (DCLS), pulse-width coded Amplitude modulated, sine wave carrier Manchester modulated CarrierFrequency / Resolution No carrier (DCLS) 100 Hz / 10 ms resolution 1 kHz / 1 ms resolution 10 kHz / 100 microsecond resolution 100 kHz / 10 microsecond resolution Coded Expressions BCDTOY, CF, SBS BCDTOY, CF BCDTOY BCDTOY, SBS BCDTOY, BCDYEAR, CF, SBS BCDTOY, BCDYEAR, CF BCDTOY, BCDYEAR BCDTOY, BCDYEAR, SBS

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TECH NOTE— Overview of IRIG-B Time Code Standard

TN-102 |

Sep-2009

IRIG-B PROTOCOL DESCRIPTION

IRIG-B Overview
IRIG time code B (IRIG-B) is widely used in the electrical power industry. IRIG-B has a pulse rate of 100 pulses-per-second with an index count of 10 milliseconds over its one-second time frame. It contains time-of-year and year information in a BCD format, and (optionally)...
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