IRIG Standard 200-04.pdf

IRIG STANDARD 200-04

TELECOMMUNICATIONS

AND TIMING GROUP

IRIG SERIAL TIME CODE FORMATS

DISTRIBUTION A: APPROVED FOR PUBLIC RELEASE

DISTRIBUTION IS UNLIMITED

WHITE SANDS MISSILE RANGE

REAGAN TEST SITE

YUMA PROVING GROUND

DUGWAY PROVING GROUND

ABERDEEN TEST CENTER

NATIONAL TRAINING CENTER

ELECTRONIC PROVING GROUND

NAVAL AIR WARFARE CENTER WEAPONS DIVISION

NAVAL AIR WARFARE CENTER AIRCRAFT DIVISION

NAVAL UNDERSEA WARFARE CENTER DIVISION, NEWPORT

PACIFIC MISSILE RANGE FACILITY

NAVAL UNDERSEA WARFARE CENTER DIVISION, KEYPORT

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BARRY M. GOLDWATER RANGE

UTAH TEST AND TRAINING RANGE

NATIONAL NUCLEAR SECURITY ADMINISTRATION (NEVADA)

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IRIG SERIAL TIME CODE FORMATS

SEPTEMBER 2004

Prepared by

TIMING COMMITTEE

TELECOMMUNICATIONS AND TIMING GROUP

RANGE COMMANDERS COUNCIL

Published by

Secretariat Range Commanders Council

U.S. Army White Sands Missile Range, New Mexico 88002-5110

THIS DOCUMENT IS AVAILABLE ON THE

RANGE COMMANDERS WEBSITE AT

http://jcs.mil/RCC http://jcs.mil/RCC/

CHANGES TO THIS EDITION

IRIG Standard 200-98 was last updated in May 1998 and defined the characteristics of the serial time codes A, B, D, E, G, and H This 2004 edition of the Standard incorporates year information for codes A, B, E, and G. Codes D and H remain unchanged. The task of revising this standard was assigned to the Telecommunications and Timing Group (TTG) of the Range Commanders Council (RCC).

All U.S. Government ranges and facilities should adhere to this standard where serial time codes are generated for correlation of data with time.

iii iv

TABLE OF CONTENTS

CHANGES TO THIS EDITION ................................................................................................ iii

LIST OF FIGURES ..................................................................................................................... vi

LIST OF TABLES ....................................................................................................................... vi

ACRONYMS AND ABBREVIATIONS.................................................................................... ix

CHAPTER 1: INTRODUCTION............................................................................................ 1-1

CHAPTER 2: GENERAL DESCRIPTION OF THIS STANDARD................................... 2-1

CHAPTER 3: GENERAL DESCRIPTION OF FORMATS ............................................... 3-1

3.1 Overview...................................................................................................................... 3-1

3.2 Time Code Formats...................................................................................................... 3-1

CHAPTER 4: DETAILED DESCRIPTION OF FORMATS .............................................. 4-1

4.1 Time Code Formats (A, B, D, E, and G) ..................................................................... 4-1

4.2 Examples Of Typical Modulated Carrier Signal Formats For IRIG A, B, E, and G... 4-2

4.3 Manchester II Coding .................................................................................................. 4-7

4.4 Manchester II Decoding............................................................................................... 4-9

CHAPTER 5: GENERAL DESCRIPTION OF TIME CODES .......................................... 5-1

5.1 Introduction.................................................................................................................. 5-1

5.2 Time Code Format A ................................................................................................... 5-1

5.3 Time Code Format B ................................................................................................... 5-1

5.4 Time Code Format D ................................................................................................... 5-2

5.5 Time Code Format E.................................................................................................... 5-2

5.6 Time Code Format G ................................................................................................... 5-3

5.7 Time Code Format H ................................................................................................... 5-3

CHAPTER 6: DETAILED DESCRIPTION OF TIME CODES......................................... 6-1

6.1 Introduction.................................................................................................................. 6-1

6.2 Format A ...................................................................................................................... 6-1

6.3 Format B ...................................................................................................................... 6-6

6.4 Format D .................................................................................................................... 6-11

6.5 Format E..................................................................................................................... 6-14

6.6 Format G .................................................................................................................... 6-19

6.7 Format H .................................................................................................................... 6-24

APPENDIX A: LEAP YEAR/LEAP SECOND CONVENTIONS ..................................... A-1

1.1 Leap Year Convention ................................................................................................ A-1

1.2 Leap Second Convention ............................................................................................ A-1

APPENDIX B: BCD COUNT/BINARY COUNT..................................................................B-1 v

APPENDIX C: HARDWARE DESIGN CONSIDERATIONS........................................... C-1

GLOSSARY

1.1 Definitions of Terms And Usage

1.2 Time-related terms and the relationship between the various time scales

LIST OF FIGURES

Figure 3-1. Typical modulated carrier signal. ........................................................................ 3-5 Figure 4-1. Serial time code formats ...................................................................................... 4-1 Figure 4-2. IRIG B coding comparisons: level shift, 1kHz am, and Modified Manchester... 4-8 Figure 4-3. Modified Manchester coding. .............................................................................. 4-8 Figure 4-4. A Manchester II Encoded Sequence .................................................................... 4-9 Figure 6-2. Format B: BCD time-of-year in days, hours, minutes, seconds and year and straight binary seconds-of-day and control bits. ................................................ 6-7 Figure 6-3. Format D: BCD time-of-year in days and hours and control bits..................... 6-12 Figure 6-4. Format E: BCD time-of-year in days, hours, minutes, seconds, and year and control bits. ........................................................................................................ 6-15 Figure 6-5. Format G: BCD Time-of-year in days, hours, minutes, seconds, and year and fractions-of-seconds, and control bits. ............................................................... 6-20 Figure 6-6. Format H: BCD time-of-year in days, hours, minutes, and control bits........... 6-25

LIST OF TABLES

Table 3-1. Bit Rates And Index Count Intervals Of The Time Code Formats...................... 3-1 Table 3-2. Time Frame Rates And Time Frame Intervals Of The Formats.......................... 3-2 Table 3-3. Position Identifiers And Index Count Locations ................................................. 3-3 Table 3-4. Number Of Available Control Bits In Each Time Code Format ......................... 3-3 Table 3-5. Typical Modulated Carrier Signal Formats For A, B, E, D, G, And H ............... 3-6 Table 4-1. Permissible Code Formats (A, B, D, E, G, H) ..................................................... 4-2 Table 4-2. Typical Modulated Carrier Signal Formats (IRIG A).......................................... 4-3 Table 4-3. Typical Modulated Carrier Signal Formats (IRIG B).......................................... 4-4 Table 4-4. Typical Modulated Carrier Signal Formats (IRIG E) .......................................... 4-5 Table 4-5. Typical Modulated Carrier Signal Formats (IRIG G).......................................... 4-6 Table 4-6: Truth Table Is A Modulo-2 Adder....................................................................... 4-9 Table 6-1. Format A, Signal A000........................................................................................ 6-3 Table 6-2. IRIG-A Control Bit Assignment For Year Information ...................................... 6-4 Table 6-3. Format A Control Functions (27 Bits) ................................................................. 6-5 Table 6-4. Parameters For Format A..................................................................................... 6-5 Table 6-5. Format B, Signal B000 ........................................................................................ 6-8 Table 6-6. IRIG-B Control Bit Assignment For Year Information....................................... 6-9 Table 6-7. Format B Control Functions (45 Bits) ............................................................... 6-10 Table 6-8. Parameters For Format B ................................................................................... 6-10 Table 6-9. Format D, Signal D001...................................................................................... 6-13 Table 6-10. Parameters For Format D................................................................................... 6-14 Table 6-11. Format E, Signal E001....................................................................................... 6-16 vi

Table 6-12. IRIG-E Control Bit Assignment For Year Information..................................... 6-17 Table 6-13. Format E Control Functions (45 Bits) ............................................................... 6-18 Table 6-14. Parameters For Format E ................................................................................... 6-18 Table 6-15. Format G, Signal G001...................................................................................... 6-21 Table 6-16. IRIG-G Control Bit Assignment For Year Information .................................... 6-22 Table 6-17. Format G Control Functions (36 Bits) ............................................................... 6-23 Table 6-18. Parameters For Format G................................................................................... 6-23 Table 6-19. Format H, Signal H001...................................................................................... 6-26 Table 6-20. Parameters For Format H................................................................................... 6-27 Table B-1. Bcd Count (8n 4n 2n 1n)......................................................................................B-1 Table B-2. Binary Count (2n).................................................................................................B-2 Table C-1. Time Code Generator Hardware Minimum Design Considerations....................C-1 vii viii

ACRONYMS AND ABBREVIATIONS

ABBREVIATIONS (by category) TERMS

CF Control Function

Hz An abbreviation for Hertz (Cycles per second) k 1000 kHz Kilohertz (1000 Hz) fph Frames per hour fpm Frames per minute fps Frames per second pph Pulses per hour ppm Pulses per minute pps Pulses per second y Year mo Month d Day h Hour m Minute s Second ms Millisecond (10-3s) µs Microsecond (10-6s) ns Nanosecond (10-9s)

DoY Day-of-year DoM Day-of-month HoD Hour-of-day MoH Minutes-of-hour SoD Seconds-of-day (86.4x103) MoD Milliseconds-of-day (86.4x106) MioD Microseconds-of-day (86.4x109)

BCD Binary coded decimal SBS Straight binary second(s) SB Straight binary

BIT B(INARY + DIG)IT

LSB Least significant bit MSB Most significant bit

NRZ-L Non return to zero level SBS Straight binary time of day (seconds of day) SB Straight binary ix x

CHAPTER 1

INTRODUCTION

Modern day electronic systems such as communication systems, data handling systems, and missile and spacecraft tracking systems require time-of-day and year information for correlation of data with time. Parallel and serial formatted time codes are used to efficiently interface the timing system output with the user system. Parallel time codes are defined in IRIG Standard 205-87, IRIG Standard Parallel Binary and Parallel Binary Coded Decimal Time Code Formats. Standardization of time codes is necessary to ensure system compatibility among the various ranges, ground tracking networks, spacecraft and missile projects, data reduction facilities, and international cooperative projects.

This standard defines the characteristics of six serial time codes presently used by the U.S. Government and private industry. Year information has been added to IRIG codes A, B, E, and G. It should be noted that this standard reflects the present state-of-the-art in serial time code formatting and is not intended to constrain proposals for new serial time codes with greater resolution.

All Department of Defense (DoD) test ranges, facilities, and other government agencies such as the National Aeronautics and Space Administration (NASA) maintain Coordinated Universal Time (UTC) referenced to the United States Naval Observatory (USNO) Master Clock. The designation for time in the United States is UTC (USNO).

1-1

1-2

CHAPTER 2

GENERAL DESCRIPTION OF THIS STANDARD

This standard consists of a family of rate-scaled serial time codes with formats containing up to four coded expressions or words. All time codes contain control functions that are reserved for encoding various controls, identification, and other special purpose functions. Time codes A, B, D, E, G, and H are described below.

• Time code A has a time frame of 0.1 seconds with an index count of 1 millisecond and contains time-of-year and year information in a binary coded decimal (BCD) format, and seconds-of-day in straight binary seconds (SBS).

• Time code B has a time frame of 1 second with an index count of 10 milliseconds and contains time-of-year and year information in a BCD format, and seconds-of-day in SBS.

• Time code D has a time frame of 1 hour with an index count of 1 minute and contains time-of- year information in days and hours in a BCD format.

• Time code E has a time frame of 10 seconds with an index count of 100 milliseconds and contains time-of-year and year information in a BCD format.

• Time code G has a time frame of 0.01 seconds with an index count of 0.1 milliseconds and contains time-of year information in days, hours, minutes, seconds, fractions of seconds and year information in a BCD format.

• Time code H has a time frame of 1 minute with an index count of 1 second and contains time-of-year information in days, hours, and minutes in a binary coded decimal BCD format.

2-1

2-2

CHAPTER 3

GENERAL DESCRIPTION OF FORMATS

3.1 Overview

A description of the time code formats is described in the subparagraphs below.

Additional reference information is provided at the end of this document on the related topics of leap year and leap second conventions (Appendix A), Binary Coded Decimal (BCD) count data and binary count data (Appendix B), and time code generator hardware design considerations (Appendix C).

3.2 Time Code Formats

3.2.1 Pulse Rise Time. The specified pulse (dc level shift bit) rise time shall be obtained between the 10 and 90 percent amplitude points (see Appendix C).

3.2.2 Jitter. The modulated code is defined as <_ 1 percent at the carrier frequency. The dc level shift code is defined as the pulse-to-pulse variation at the 50 percent amplitude points on the leading edges of successive pulses or bits (see Appendix C).

3.2.3 Bit Rates and Index Count. Each pulse in a time code word/sub-word is called a bit. The "on-time" reference point for all bits is the leading edge of the bit. The repetition rate at which the bits occur is called the bit rate. Each bit has an associated numerical index count identification. The time interval between the leading edge of two consecutive bits is the index count interval. The index count begins at the frame reference point with index count 0 and increases one count each index count until the time frame is complete.

The bit rates and index count intervals of the time code formats are shown in Table 3-1.

TABLE 3-1. BIT RATES AND INDEX COUNT INTERVALS OF THE TIME CODE

FORMATS

Format Bit Rate1 Index Count Interval A 1 kpps 1 millisecond B 100 pps 10 milliseconds D 1 ppm 1 minute E 10 pps 0.1 second G 10 kpps 0.1 millisecond H 1 pps 1 second

1 See the abbreviations and acronyms page at the beginning of this document for bit rate definitions

3.2.4 Time Frame, Time Frame Reference, and Time Frame Rates. A time code frame begins with a frame reference marker P0 (position identifier) followed by a reference bit Pr with each having duration equal to 0.8 of the index count interval of the respective code. The on-time

3-1 reference point of a time frame is the leading edge of the reference bit Pr. The repetition rate at which the time frames occur is called the time frame rate. The time frame rates and time frame intervals of the formats are shown in Table 3-2.

TABLE 3-2. TIME FRAME RATES AND TIME FRAME INTERVALS OF THE

Format Time Frame Rate Time Frame Interval

A 10 fps 0.1 second B 1 fps 1 second D 1 fph 1 hour E 6 fpm 10 seconds G 100 fps 10 ms H 1 fpm 1 minute

3.2.5 Position Identifiers. Position identifiers have durations equal to 0.8 of the index count interval of the respective code. The leading edge of the position identifier P0 occurs one index count interval before the frame reference point Pr and the succeeding position identifiers (P2, P2...P0) occur every succeeding tenth bit. The repetition rate at which the position identifiers occur is always 0.1 of the time format bit rate.

3.2.6 Time Code Words. The two time code words employed in this standard are:

• Binary Coded Decimal (BCD) time-of-year and year

• Straight Binary Seconds (SBS) time-of-day (seconds-of-day)

All time code formats are pulse-width coded. A binary (1) bit has duration equal to 0.5 of the index count interval, and a binary (0) bit has duration equal to 0.2 of the index count interval. The BCD time-of-year code reads 0 hours, minutes, seconds, and fraction of seconds at 2400 each day and reads day 001 at 2400 of day 365 or day 366 in a leap year. The year code counts year and cycles to the next year on January 1st of each year and will count to year 2099.

The SBS time-of-day code reads 0 seconds at 2400 each day excluding leap second days when a second may be added or subtracted.

3.2.7 BCD Time-of-Year Code Word. The BCD time-of-year and year code word consists of sub-words in days, hours, minutes, seconds, and year with fractions of a second in a BCD representation and time-of-day in SBS of day. The position identifiers preceding the decimal digits and the index count locations of the decimal digits (if present) are in Table 3-3.

Formats A and B include an optional SBS time code word in addition to a BCD time-of-year time and year code word. The SBS word follows position identifier P8 beginning with the least significant binary bit (20) at index count 80 and progressing to the most significant binary bit (216) at index count 97 with a position identifier P9 occurring between the ninth (28) and tenth (29) binary bits. Codes A, B, E, and G also contain year information in a BCD format and are an extension to the time-of-year format.

3-2

TABLE 3-3. POSITION IDENTIFIERS AND INDEX COUNT LOCATIONS

BCD Code Decimal Digits Decimal Digits Follow Position Identifier

Digits Occupy Index Count Positions

Units of seconds Tens of Seconds

P0 1-4 6-8

Units of Minutes Tens of Minutes

P1 10-13 15-17

Units of Hours Tens of Hours

P2 20-23 25-26

Units of Days Tens of Days

P3 30-33 35-38

Hundreds of Days Tenths of Seconds

P4 40-41 45-48

Hundredths of Seconds

P5 50-53

For Codes A, B, and E Tens of Years Hundredths of Years

P5 51-54 56-59

For Code G Tens of Year Hundredths of Year

P6 61-64 66-69

3.2.8 Control Functions. All time code formats reserve a set of bits known as control functions (CF) for the encoding of various control, identification, and other special purpose functions. The control bits may be programmed in any predetermined coding system. A binary 1 bit has duration equal to 0.5 of the index count interval, and a binary (0) bit has duration equal to 0.2 of the index count interval. Control function bits follow position identifiers P5, P6 or P7 for formats A, B, E, and G beginning at index count 50, 60 or 70 with one control function bit per index count, except for each tenth bit which is a position identifier. The number of available control bits in each time code format is shown at Table 3-4.

TABLE 3-4. NUMBER OF AVAILABLE CONTROL BITS IN EACH TIME CODE

FORMAT

Format Control Functions A 18 B 18 D 9 E 36 G 27 H 9

3-3

Control functions are presently intended for internal range use, but not for interrange applications; therefore, no standard coding system exists. The inclusion of control functions into a time code format as well as the coding system employed is an individual user defined option.

3.2.9 Index Markers. Index markers occur at each index count position, which is not assigned as a reference marker, position identifier, code, or control function bit. Each index marker bit has duration equal to 0.2 of the index count interval of the respective time code format.

3.2.10 Amplitude Modulated Carrier. A standard sine wave carrier frequency to be amplitude modulated by a time code is synchronized to have positive-going, zero-axis crossings coincident with the leading edges of the modulating code bits. A mark-to-space ratio of 10:3 is standard with a range of 3:1 to 6:1 (see Typical Modulated Carrier Signal descriptions at Figure 3-1 and Table 3-5).

3-4

3-5

Figure 3-1. Typical modulated carrier signal.

TABLE 3-5. TYPICAL MODULATED CARRIER SIGNAL FORMATS FOR A, B, E, D, G, AND H

MARK INTERVAL

NUMBER OF CYCLES

FORMAT

SIGNAL NO.

TIME

FRAME

RATE

CARRIER

FREQUENCY

F

SIGNAL

BIT RATE

ER

RATIO

F/ER

CODE "0"

INDEX

CODE "1"

POSITION

IDENTIFIER

& REF.

A A130, 132 133, 134

10 per sec. 10 kHz 1 kpps 10:1 2 5 8

B B120, 122 123, 127

1 per sec. 1 kHz 100 pps 10:1 2 5 8

D D111, 112 121,122

1 per hr. 100Hz 1kHz

1 ppm 1 ppm

6000:1 60000:1

12000

30000

48000

E E111, 112 121,122, 125

6 per min 100Hz 1kHz

10 pps 10 pps

10:1 100:1

G G141, 142, 126 100 per sec. 100 kHz 10 kpps 10:1 2 5 8

H H111, 112 121,122

1 per min. 100 Hz 1 kHz

1 pps 1 pps

100:1 1000:1

3-6

CHAPTER 4

DETAILED DESCRIPTION OF FORMATS

4.1 Time Code Formats (A, B, D, E, and G)

4.1.1 Serial Time Code Formats. The family of rate-scaled serial time code formats is designated A, B, D, E, G, and H. Various combinations of sub-words and signal forms make up a time code word. All formats do not contain each standard coded expression, and various signal forms are possible. To differentiate between these forms, signal identification numbers are assigned to each permissible combination (see Figure 4-1).

Format:

Format A 1 k pps

Format B 100 pps Format D 1 ppm Format E 10 pps Format G 10 k pps Format H 1 pps

Modulation Frequency:

0 Pulse width code 1 Sine wave, amplitude modulated

2 Manchester modulated

Frequency/Resolution:

0 No carrier/index count interval

1 100 Hz/10 ms 2 1 kHz/1 ms

3 10 kHz/0.1 ms 4 100 kHz/10 ms 5 1 MHz/1ms

Coded Expressions:

0 BCDTOY, CF, SBS

1 BCDTOY, CF

2 BCDTOY

3 BCDTOY, SBS

4 BCDTOY, BCDYEAR, CF, SBS

5 BCDTOY, BCDYEAR, CF

6 BCDTOY, BCDYEAR

7 BCDTOY, BCDYEAR, SBS

A 1 3 7

The signal designated as A137 is deciphered as follows: Format A, Sine wave (amplitude modulated), 10 kHz carrier/0.1 ms resolution, and Coded expressions BCDTOY, BCDYEAR, and SBS.

Figure 4-1. Serial time code formats

4-1

4.1.2 Manchester Time Code Formats. The resolution of a time code is that of the smallest increment of time or the least significant bit that can be defined by a time code word or sub-word. The accuracy of a modified, Manchester time code can be determined by the rise-time of the on-time pulse in the Manchester code which marks the beginning of the on-time one-pulse-per-second as shown in Figure 3-1 above. The accuracy can range from milliseconds to nanoseconds or better depending on equipment and measurement technique. For the case of the unmodulated Manchester codes, the Position Marker PO, which marks the beginning of the second, can be used.

The information in Table 4-1 shows the permissible code formats. Codes D, and H remain unchanged. Codes A, B, E and G have changed to permit year information as indicated below. No other combinations are standard.

TABLE 4-1. PERMISSIBLE CODE FORMATS (A, B, D, E, G, H)

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, 2, 3, 4, 5

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

D

0, 1

1, 2

E

1, 2, 5, 6

G

0, 4, 5

1, 2, 5, 6

H

1, 2

The Telecommunications and Timing Group (TTG) of the Range Commanders Council (RCC) has adopted a Modified Manchester modulation technique as an option for the IRIG serial time codes A, B, and G as an addition to the standard AM modulation and level shift modulation now permitted. Also, year information has been added to codes A, B, E, and G. Codes D and H remain unchanged. It should be noted that at present, the assignment of control bits (control functions) to specific functions in the IRIG serial time codes is left to the end-user of the time codes.

4.2 Examples Of Typical Modulated Carrier Signal Formats For IRIG A, B, E, and G

Examples are provided on the following pages as follows:

IRIG A: Table 4-2 IRIG B Table 4-3 IRIG E Table 4-4 IRIG G Table 4-5

4-2

TABLE 4-2. TYPICAL MODULATED CARRIER SIGNAL FORMATS (IRIG A)

Modified Manchester Modulations1

A 237 2 = Manchester modulation 3 = 10 kHz/0.1 ms

7 = BCDTOY, BCDYEAR, SBS

Standard AM modulations (Example Formats)

A130 1 = Sine wave, amplitude modulated 3 = 10 kHz/0.1 ms

0 = BCDTOY, CF, SBS

A 134 1 = Sine wave, amplitude modulated 3 = 10 Khz/0.1 ms

4 = BCDTOY, BCDYEAR, CF, SBS

A 132 1 = Sine wave, amplitude modulated 3 = 10 kHz/0.1 ms

2 = BCDTOY

A 136 1 = Sine wave, amplitude modulated 3 = 10 kHz/0.1 ms

6 = BCDTOY, BCDYEAR

A 133 1 = Sine wave, amplitude modulated 3 = 10 kHz/0.1 ms

3 = BCDTOY, SBS

A 137 1 = Sine wave, amplitude modulated 3 = 10 kHz/0.1ms

7 = BCDTOY, BCDYEAR, SBS

A 131 1 = Sine wave, amplitude modulated 3 = 10 kHz/0.1ms

1 = BCDTOY, CF

A 135 1 = Sine wave, amplitude modulated 3 = 10 kHz/0.1 ms

5 = BCDTOY, BCDYEAR, CF

1Modified Manchester modulation is an option for IRIG A in addition to the standard AM modulation in the formats in this table

4-3

TABLE 4-3. TYPICAL MODULATED CARRIER SIGNAL FORMATS (IRIG B)

B 237 2 = Manchester modulation 3 = 10 kHz/0.1 ms

7 = BCDTOY, BCDYEAR, SBS

Standard AM modulations (Example Formats)

B120 1 = Sine wave, amplitude modulated 2 = 1 kHz/1 ms

0 = BCDTOY, CF, SBS

B 124 1 = Sine wave, amplitude modulated 2 = 1 kHz/1 ms

4 = BCDTOY, BCDYEAR, CF, SBS

B 121 1 = Sine wave, amplitude modulated 2 = 1 kHz/1 ms

1 = BCDTOY, CF

B 125 1 = Sine wave. Amplitude modulated 2 = 1 kHz/1 ms

5 = BCDTOY, BCDYEAR, CF

B 122 1 = Sine wave, amplitude modulated 2 = 1 kHz/1 ms

2 = BCDTOY

B 126 1 = Sine wave, amplitude modulated 2 = 1 kHz/1 ms

6 = BCDTOY, BCDYEAR

B 123 1 = Sine wave, amplitude modulated 2 = 1 kHz/1 ms

3 = BCDTOY SBS

B 127 1 = Sine wave, amplitude modulated 2 = 1 kHz/1 ms

7 = BCDTOY, BCDYEAR, SBS

1Modified Manchester modulation is an option for IRIG B in addition to the standard AM modulation in the formats in this table.

4-4

TABLE 4-4. TYPICAL MODULATED CARRIER SIGNAL FORMATS (IRIG E)

Standard AM modulations (Example Formats)

E 111 1 = Sine wave, amplitude modulated 1 = 100 Hz/10 ms

1 = BCDTOY, CF

E115 1 = Sine wave, amplitude modulated 1 = 100 Hz/10 ms

5 = BCDTOY, BCDYEAR, CF

E 112 1 = Sine wave, amplitude modulated 1 = 100 Hz/10 ms

2 = BCDTOY,

E 116 1 = Sine wave, amplitude modulated 1 = 100 Hz/10 ms

6 = BCDTOY, BCDYEAR

E 121 1 = Sine wave, amplitude modulated 2 = 1kHz/1 ms

1 = BCDTOY, CF

E 125 1 = Sine wave, amplitude modulated 2 = 1kHz/1 ms

5 = BCDTOY, BCDYEAR, CF

E 122 1 = Sine wave, amplitude modulated 2 = 1kHz/1 ms

2 = BCDTOY

E 126 1 = Sine wave, amplitude modulated 2 = 1kHz/1ms

6 = BCDTOY, BCDYEAR

4-5

TABLE 4-5. TYPICAL MODULATED CARRIER SIGNAL FORMATS (IRIG G)

G 245 2 = Manchester modulation

4 = 100 kHz/10 ms

5 = BCDTOY, BCDYEAR, CF

Standard AM modulations (Example Formats)

G 141 1 = Sign wave, amplitude modulation

1 = BCDTOY, CF

G 145 1 = Sign wave, amplitude modulation

5 = BCDTOY, BCDYEAR, CF

G 142 1 = Sign wave, amplitude modulated

2 = BCDTOY

G 146 1 = Sign wave, amplitude modulated

6 = BCDTOY, BCDYEAR

1Modified Manchester modulation is an option for IRIG G in addition to the standard AM modulation in the formats in this table

4-6

4.3 Manchester II Coding

Standard Manchester modulation or encoding is a return-to-zero type, where a rising edge in the middle of the clock window indicates a binary one (1) and a falling edge indicates a binary zero (0). This modification to the Manchester code shifts the data window so the data are at the edge of the clock window that is on time with the one-pulse-per-second clock synchronized to Coordinated Universal Time (UTC). Thus, the data edge is the on-time mark in the code.

Because this code is easy to generate digitally, easy to modulate onto fiber or coaxial cable, simple to decode, and has a zero mean, and the code is easy to detect even at low voltage levels.

The basic Modified Manchester modulation, compared with the AM and level shift modulations are shown at Figure 4-2 and Figure 4-3. The Manchester encoding uses a square-wave as the encoding (data) clock, with the rising edge on time with UTC. The frequency of the encoding clock shall be ten times the index rate of the time code generated. As an example, the clock rate for IRIG B230 shall be 10 kHz.

The Modified Manchester coding technique has several advantages as noted below.

• No dc component

• Can be ac coupled

• Better signal-to-noise ratio

• Good spectral power density

• Easily decoded

• Better timing resolution

• The link integrity monitoring capability is intrinsic to bipolar pulse modulation.

• The coding technique is designed to operate over fiber-optic or coaxial lines for short distances.

4-7

Figure 4-2. IRIG B coding comparisons: level shift, 1kHz am, and Modified Manchester.

Figure 4-3. Modified Manchester coding.

4-8

4.4 Manchester II Decoding

An example of a Manchester II encoded sequence is shown at Figure 4-4, where each symbol is “sub-bit” encoded, i.e., a data one equals a zero-one, and a data zero equals a one-zero:

Figure 4-4. A Manchester II Encoded Sequence

The encoded sequence at Figure 4-4 is formed by modulo-2 adding the NRZ-L sequence with the clock. The truth table shown in Table 4-6 is for a modulo-2 adder, which is equivalent to an Exclusive-OR (XOR).

TABLE 4-6: TRUTH TABLE IS A MODULO-2 ADDER

INPUT A

INPUT B

OUTPUT

To decode the encoded sequence of Figure 4-4, it is only necessary to modulo-2 add the clock with the encoded sequence and the original NRZ-L sequence results. It should be noted that the bit determination is made after integrating across a bit period. In this way, the maximum amount of bit energy is used in the determination of each bit. Likewise, one could have integrated or sampled both halves of the encoded sequence and reconstructed the original Non Return To Zero Level (NRZ-L) sequence by applying the encoding rule. This means that if sampled halves are 0-1, then a data 1 is reconstructed, and if the sampled halves are 1-0, then a data 0 is reconstructed. Once again, as much energy as possible is used from the encoded

4-9 sequence to reconstruct the original NRZ-L sequence. This procedure minimizes the probability of error.

NOTE

When the above procedure is used, the reconstructed data are coherent with the clock; that is, the NRZ-L data transitions will agree with the positive going edge of the clock. However, since the decisions are made at the end of the symbol period, the reconstructed NRZ-L data are delayed one clock period; this means that when the entire time is received, the received time code or local clock needs to be advanced by one clock period. Also, if desired, one can correct the receive clock for significant signal propagation delays.

4-10

CHAPTER 5

GENERAL DESCRIPTION OF TIME CODES

5.1 Introduction

A general description of individual time code formats is described in the following sub-paragraphs. Year information has been added to formats A, B, E and G in 1, 2, 4, 8 and 10, 20, 40, 80 BCD bits using the unassigned Control Function (CF) BITs. This permits a year count from 2000 to 2099. If users desire the “Century Year” information, they can use two binary coded decimal BCD CF bits with a value of 0, 2, and 3. Therefore, a user wanting to start with year 2000 can count to year 2399.

5.2 Time Code Format A

5.2.1 The 78-bit time code contains 34 bits of BCD time-of-year information in days, hours, minutes and tenths of seconds, 17 bits of straight binary seconds-of-day (SBS), and 9 bits for year information in BCD. The remaining 18 bits are for control functions.

5.2.2 The BCD code (seconds sub-word) begins at index count 1 (LSB first) with binary coded bits occurring between position identifier P0 and P5. There are 7 bits for seconds, 7 for minutes, 6 for hours, 10 for days, 4 for tenths of seconds, and 9 for year information between position identifiers P5 and P6 to complete the BCD word. An index marker occurs between the decimal digits in each sub-word, except for the tenths of seconds, to provide for visual separation. The BCD time-of-year code recycles yearly.

5.2.3 The SBS word begins at index count 80 and is between position identifiers P8 and P0 with a position identifier bit, P9 between the 9th and 10th binary SBS coded bits. The SBS time code recycles each 24-hour period.

5.2.4 The eighteen control bits occur between position identifiers P6 and P8 with a position identifier occurring every 10 bits.

5.2.5 The frame rate or repetition rate is 0.1 seconds with resolutions of 1 ms (dc level shift) and 0.1 ms (modulated 10 kHz carrier).

5.3 Time Code Format B

5.3.1 The 74-bit time code contains 30 bits of BCD time-of-year information in days, hours, minutes and seconds, 17 bits of SB seconds-of-day, 9 bits for year information and 18 bits for control functions.

5.3.2 The BCD code (seconds sub-word) begins at index count 1 (LSB first) with binary coded bits occurring between position identifier bits P0 and P6: 7 for seconds, 7 for minutes, 6 for hours, 10 for days and 9 for year information between position identifiers P5 and P6 to complete the BCD word. An index marker occurs between the decimal digits in each sub-word to provide separation for visual resolution.

5-1

5.3.3 The SBS word begins at index count 80 and is between position identifiers P8 and P0 with a position identifier bit, P9 between the 9th and 10th SBS coded bits. The SBS time code recycles each 24-hour period.

5.3.4 The eighteen control bits occur between position identifiers P6 and P8 with a position identifier every 10 bits.

5.3.5 The frame rate is 1.0 seconds with resolutions of 10 ms (dc level shift) and 1 ms (modulated 1 kHz carrier).

5.4 Time Code Format D

5.4.1 The 25-bit time code contains 16 bits of BCD Time-of-year information in days, hours, minutes and 9 bits for control functions.

5.4.2 The BCD code (hours sub-word) begins at index count 20 (LSB first) with binary coded bits occurring between position identifier bits P2 and P5: 6 for hours and 10 for days to complete the BCD word. An index marker occurs between the decimal digits in each sub-word for visual resolution. The BCD time-of-year code recycles yearly.

5.4.3 The nine control bits occur between position identifiers P5 and P0.

5.4.4 The frame rate is one hour with resolutions of 1 minute (dc level shift), 10 ms (modulated 100 Hz carrier) and 1 ms (modulated 1 kHz carrier).

5.5 Time Code Format E

5.5.1 The 71-bit time code contains 26 bits of BCD time-of-year information in days, hours, minutes, and seconds, 9 bits for year information, and 36 bits for control functions between position identifiers P6 and P0.

5.5.2 The BCD code (seconds sub-word) begins at index count 6 (LSB first). Binary coded Bits occur between position identifiers P0 and P5: 3 bits for tens of seconds, 7 for minutes, 6 for hours, 10 for days and 9 bits for year information between position identifiers P5 and P6 to complete the BCD word. An index marker occurs between the decimal digits in each sub-word to provide visual resolution. The BCD time-of-year code recycles yearly.

5.5.3 The eighteen control bits occur between position identifiers P6 and P0.

5.5.4 The frame rate is 10 seconds with resolutions of 0.1 seconds (dc level shift), 10 ms (modulated 100 Hz carrier), and 1 ms (modulated 1 kHz carrier).

5-2

5.6 Time Code Format G

5.6.1 The 74-bit time code contains 38 bits of BCD time-of-year information in days, hours, minutes, seconds, and fraction of seconds, 9 bits of year information, and 27 bits for control functions.

5.6.2 The BCD code (seconds sub-word) begins at index count 1 (LSB first). Binary coded bits occur between position identifiers P0 and P6: 7 bits for seconds, 7 for minutes, 6 for hours, 10 for days, 4 for tenths of seconds, 4 for hundredths of seconds and 9 for year information between position identifiers P6 and P7 to complete the BCD word. An index marker occurs between the decimal digits in each sub-word (except fractional seconds) to provide for visual resolution. The BCD time-of-year code recycles yearly.

5.6.3 The twenty-seven control bits occur between position identifiers P7 and P0.

5.6.4 The frame rate is 10 ms with resolutions of 0.1 ms (dc level shift) and 10s (100 kHz carrier).

5.7 Time Code Format H

5.7.1 The 32-bit time code word contains 23 bits of BCD time-of-year information in days, hours, and minutes and 9 bits for control functions.

5.7.2 The BCD code (minutes sub-word) begins at index count 10 (LSB first) with binary coded bits occurring between position identifier bits P1 and P5: 7 bits for minutes, 6 for hours, and 10 for days to complete the BCD word. An index marker occurs between decimal digits in each sub-word to provide separation for visual resolution. The time code recycles yearly.

5.7.3 The nine control bits occur between position identifiers P5 and P0.

5.7.4 The frame rate is 1 minute with resolutions of 1 second (dc level shift), 10 ms (modulated 100 Hz carrier) and 1 ms (modulated 1 kHz carrier).

5-3

5-4

CHAPTER 6

DETAILED DESCRIPTION OF TIME CODES

6.1 Introduction

Detailed descriptions of individual time code formats are shown in the following paragraphs.

6.2 Format A

6.2.1 The beginning of each 0.1 second time frame is identified by two consecutive 0.8 ms bits, P0 and Pr. The leading edge of Pr is the on-time reference point for the succeeding time code words. Position identifiers, P0 and P1 through P9, (0.8 ms duration) occur every 10th bit and 1 ms before the leading edge of each succeeding 100 pps on-time bit (see Figure 6-1).

6.2.2 The three time code words and the control functions presented during the time frame are pulse width coded. The binary zero and index markers have duration of 0.2 ms, and the binary one has duration of 0.5 ms. The 1 k pps leading edge is the on-time reference point for all bits.

6.2.3 The binary coded decimal (BCD) time-of-year coded word consists of 34 bits beginning at index count one. The time-of-year sub-word bits occur between position identifiers P0 and P5:

7 bits for seconds, 7 for minutes, 6 for hours, 10 for days, 4 for tenths of seconds. Nine bits for year information occur between position identifiers P5 and P6 to complete the BCD time code word. An index marker occurs between the decimal digits in each sub-word, except tenths of seconds, to provide separation for visual resolution. The LSB occurs first except for the fractional seconds sub-word that follows the day-of-year sub-word. The BCD time-of-year code recycles yearly.

6.2.4 Eighteen control bits occur between position identifiers P6 and P8. Any control function bit or combination of bits can be programmed to read a binary one or a binary zero during any specified number of frames. Each control bit position is identified in Table 6-1.

6.2.5 The straight binary (SB) seconds-of-day code word occurs at index count 80 between position identifiers P8 and P0. Seventeen bits give time-of-day in seconds with the LSB occurring first. A position identifier occurs between the 9th and 10th binary seconds. The code recycles each 24-hour period.

6.2.6 Control bit assignments, functions, and parameters for time code Format A are shown on the following pages as:

Table 6-2: Identifies the control bit assignments for year information.

Table 6-3: Identifies the control functions (for 27 bits).

Table 6-4: Identifies the parameters that characterize the time code for Format A.

6-1

6-2

6-2

Figure 6-1. Format A: BCD time-of-year in days, hours, minutes, seconds, fractions of seconds and year, and straight binary seconds-of-day and control bits.

TABLE 6-1. FORMAT A, SIGNAL A000

BCD TIME-OF-YEAR CODE (34 DIGITS)

SECONDS SUBWORD MINUTES SUBWORD HOURS SUBWORD DAYS AND FRACTIONAL SECOND SUBWORDS

BCD

Code

Digit No.

Subword Digit Wt

SECONDS

BIT Time (Note 1)

BCD

Code

Digit No.

Subword Digit Wt

MINUTES

BIT Time BCD Code

Digit No.

Subword Digit Wt

HOURS

BIT Time BCD Code Digit No.

Subword Digit Wt

DAYS

BIT Time BCD Code Digit No.

Subword Digit Wt

DAYS

BIT Time

Reference BIT Pr 8 1 Pr + 10 ms 15 1 Pr + 20 ms 21 1 Pr + 30 ms 29 100 Pr + 40 ms

1 1 Pr + 1 ms 9 2 Pr + 11 ms 16 2 Pr + 21 ms 22 2 Pr + 31 ms 30 200 Pr + 41 ms

2 2 Pr + 2 ms 10 4 Pr + 12 ms 17 4 Pr + 22 ms 23 4 Pr + 32 ms Index BIT Pr + 42 ms

3 4 Pr + 3 ms 11 8 Pr + 13 ms 18 8 Pr + 23 ms 24 8 Pr + 33 ms Index BIT Pr + 43 ms

4 8 Pr + 4 ms Index BIT Pr + 14 ms Index BIT Pr + 24 ms Index BIT Pr + 34 ms Index BIT Pr + 44 ms

Index BIT Pr + 5 ms 12 10 Pr + 15 ms 19 10 Pr + 25 ms 25 10 Pr + 35 ms 31 0.1 Pr + 45 ms

5 10 Pr + 6 ms 13 20 Pr + 16 ms 20 20 Pr + 26 ms 26 20 Pr + 36 ms 32 0.2 Pr + 46 ms

6 20 Pr + 7 ms 14 40 Pr + 17 ms Index BIT Pr + 27 ms 27 40 Pr + 37 ms 33 0.4 Pr + 47 ms

7 40 Pr + 8 ms Index BIT Pr + 18 ms Index BIT Pr + 28 ms 28 80 Pr + 38 ms 34 0.8 Pr + 48 ms

Position Ident. (P1) Pr + 9 ms Position Ident. (P2) Pr + 19 ms Position Ident. (P3) Pr + 29 ms Position Ident. (P4) Pr + 39 ms Position Ident. (P5) Pr + 49 ms

YEAR AND CONTROL FUNCTIONS (27 BITS) STRAIGHT BINARY SECONDS TIME-OF-DAY CODE (17 DIGITS)

Control Function

BIT

BIT Time Control Function BIT

BIT Time Control Function BIT

BIT Time SB Code

BIT

Subword Digit Weight

BIT

Time

SB Code

BIT

Subword Digit

Weight

BIT Time

1 Pr + 50 ms Units of Year

10 Pr + 60 ms 19 Pr + 70 ms 1 20 = (1) Pr + 80 ms 10 29 = (512) Pr + 90 ms

2 Units of Year

11 Pr + 61 ms 20 Pr + 71 ms 2 21 = (2) Pr + 81 ms 11 210 = (1024) Pr + 91 ms

3 Units of Year

12 Pr + 62 ms 21 Pr + 72 ms 3 22 = (4) Pr + 82 ms 12 211 = (2048) Pr + 92 ms

4 Units of Year

13 Pr + 63 ms 22 Pr + 73 ms 4 23 = (8) Pr + 83 ms 13 212 = (4096) Pr + 93 ms

5 Pr + 54 ms 14 Pr + 64 ms 23 Pr + 74 ms 5 24 = (16) Pr + 84 ms 14 213 = (8192) Pr + 94 ms

6 Tens of Year 10 15 Pr + 65 ms 24 Pr + 75 ms 6 25 = (32) Pr + 85 ms 15 214=(16384) Pr + 95 ms

7 Tens of Year 20 16 Pr + 66 ms 25 Pr + 76 ms 7 26 = (64) Pr + 86 ms 16 215=(32768) Pr + 96 ms

8 Tens of Year 40 17 Pr + 67 ms 26 Pr + 77 ms 8 27 = (128) Pr + 87 ms 17 216=(65536) Pr + 97 ms

9 Tens of Year 80 18 Pr + 68 ms 27 Pr + 78 ms 9 28 = (256) Pr + 88 ms Index BIT Pr + 98 ms

Position Ident. (P6)

Pr + 59 ms Position Ident.

(P7)

Pr + 69 ms Position Ident.

(P8)

Pr + 79 ms Position Ident. (P9) Pr + 89 ms Position Ident. (P0) Pr + 99 ms

6-3

Note 1. The BIT Time is the time of the BIT leading edge and refers to the leading edge of Pr.

TABLE 6-2. IRIG-A CONTROL BIT ASSIGNMENT FOR YEAR

INFORMATION

POS. ID CTRL BIT NO DESIGNATION EXPLANATION

P0 to P5 is BCD Time-of-year in seconds, minutes, hours, days, and fractional seconds.

P49 -- P5 Position Identifier # 5 P50 1 Year, BCD 1 Last 2 digits of year in BCD P51 2 Year, BCD 2 IBID P52 3 Year, BCD 4 IBID P53 4 Year, BCD 8 IBID P54 5 Not Used Unassigned P55 6 Year, BCD 10 Last 2 digits of year in BCD P56 7 Year, BCD 20 IBID P57 8 Year, BCD 40 IBID P58 9 Year, BCD 80 IBID P59 -- P6 Position Identifier # 6 P60 10 Not Used Unassigned

P61 11 IBID IBID

P62 12 IBID IBID

P63 13 IBID IBID

P64 14 IBID IBID

P65 15 IBID IBID

P66 16 IBID IBID

P67 17 IBID IBID

P68 18 IBID IBID

P69 -- P7 Position Identifier # 7 P70 19 Not Used Unassigned

P71 20 IBID IBID

P72 21 IBID IBID

P73 22 IBID IBID

P74 23 IBID IBID

P75 24 IBID IBID

P76 25 IBID IBID

P77 26 IBID IBID

P78 27 IBID IBID

P79 -- P8 Position Identifier # 8 P6 to P8 are control functions P8 to P0 is Time-of-Day in Straight Binary Seconds.

6-4

TABLE 6-3. FORMAT A CONTROL FUNCTIONS (27 BITS)

Function

BIT

BIT Time

Units of Year 01

Pr + 50 ms

Pr + 60 ms

Pr + 70 ms

Units of Year 02

Pr + 61 ms

Pr + 71 ms

Units of Year 04

Pr + 62 ms

Pr + 72 ms

Units of Year 08

Pr + 63 ms

Pr + 73 ms

Pr + 54 ms

Pr + 64 ms

Pr + 74 ms

Tens of Year 10

Pr + 65 ms

Pr + 75 ms

Tens of Year 20

Pr + 66 ms

Pr + 76 ms

Tens of Year 40

Pr + 67 ms

Pr + 77 ms

Tens of Year 80

Pr + 68 ms

Pr + 78 ms

Position

Ident. (P6)

Pr + 59 ms

Ident. (P7)

Pr + 69 ms

Ident (P8)

Pr + 79 ms

N ote: The BIT Time is the time of the BIT leading edge and refers to the leading edge of Pr.

TABLE 6-4. PARAMETERS FOR FORMAT A

Pulse Rates Pulse Duration

Bit rate: 1 k pps Position identifier rate: 100 pps Reference marker: 10 pps

Index marker: 0.2 ms Binary zero or unencoded bit: 0.2 ms Binary one or coded bit: 0.5 ms Position identifiers: 0.8 ms Reference bit: 0.8 ms

Resolution Mark-To-Space Ratio

1 ms dc level

0.1 ms modulated 10 kHz carrier

Nominal value of 10:3 Range of 3:1 to 6:1

6-5

6.3 Format B

6.3.1 The beginning of each 1.0 second time frame is identified by two consecutive 8.0 ms bits, P0 and Pr. The leading edge of Pr is the on-time reference point for the succeeding time code words. Position identifiers, P0 and P1 through P9, (8 ms duration) occur every 10th bit and 10 ms before the leading edge of each succeeding 10 pps "on-time" bits (see Figure 6-2).

6.3.2 The three time code words and the control functions presented during the time frame are pulse width coded. The binary zero and the index markers have duration of 2.0 ms, and a binary one has duration of 5.0 ms. The 100 pps leading edge is the on-time reference point for all bits.

6.3.3 The BCD time-of-year code word consists of 30 bits beginning at index count one. The sub-word bits occur between position identifiers P0 and P5; there are 7 bits for seconds, 7 for minutes, 6 for hours, and 10 for days. Nine bits for year information occur between position identifiers P5 and P6 to complete the BCD time code word. An index marker occurs between the decimal digits in each sub-word to provide separation for visual resolution. The LSB occurs first. The BCD time-of-year code recycles yearly. Each bit position is identified in Table 6-5.

6.3.4 Eighteen control functions occur between position identifiers P6 and P8. Any control function bit or combination of bits can be programmed to read a binary one or zero during any specified number of time frames.

6.3.5 The SB seconds-of-day word occurs between position identifier P8 and P0. A position identifier occurs between the 9th and 10th binary coded bit. The code recycles each 24-hour period.

6.3.6 Control bit assignments, functions, and parameters for time code format B are shown on

Table 6-6: Identifies the control bit assignments for year information.

Table 6-7: Identifies the control functions (for 27 bits).

Table 6-8: Identifies the parameters that characterize the time code for Format A.

6-6

6-7

Figure 6-2. Format B: BCD time-of-year in days, hours, minutes, seconds and year and straight binary seconds-of-day and control bits.

TABLE 6-5. FORMAT B, SIGNAL B000

BCD TIME-OF-YEAR CODE (30 DIGITS)

SECONDS SUBWORD MINUTES SUBWORD HOURS SUBWORD DAYS SUBWORD

BCD Code Digit No.

Subword Digit Wt

SECONDS

BIT Time (Note 1)

BCD

Code

Digit No.

BIT Time BCD Code Digit No.

Subword Digit Wt

HOURS

BIT Time Subword Digit Wt

DAYS

BIT Time BCD Code

Digit No.

Subword Digit Wt

DAYS

Reference BIT Pr 1 Pr + 100 ms 15 P + 200 ms r 21 1 r 29 100 P + 400 ms

1 1 P + 10 ms 9 Pr + 110 ms

BIT Time BCD Code

Digit No.

Subword Digit Wt

MINUTES

8 1 P + 300 ms r

2 16 2 r P + 210 ms r 22 P + 310 ms r 30 200 P + 410 ms r

2 2 P + 20 ms r 10 4 P + 120 ms r 17 4 P + 220 ms r 23 4 P + 320 ms r Index BIT r

3 4 P + 30 ms r 11 8 P + 130 ms r 18 8 P + 230 ms r 24 8 P + 330 ms r Index BIT P + 430 ms r

4 8 P + 40 ms r Index BIT Pr + 140 ms P + 240 ms r Index BIT P + 340 ms r Index BIT P + 440 ms r

Index BIT P + 50 ms r 12 10 P + 150 ms r 19 10 Pr + 250 ms 25 10 P + 350 ms r Index BIT Pr + 450 ms

P + 420 ms

Index BIT

5 10 Pr + 60 ms 13 20 Pr + 160 ms 20 20 Pr + 260 ms 26 20 Pr + 360 ms Index BIT Pr + 460 ms

6 20 Pr + 70 ms 14 40 Pr + 170 ms Index BIT r 27 40 Pr + 370 ms Index BIT Pr + 470 ms

7 40 Pr + 80 ms Index BIT Pr + 180 ms Index BIT Pr + 280 ms 28 80 Pr + 380 ms Index BIT Pr + 480 ms

Position Ident. (P1) Pr + 90 ms Position Ident. (P2) Pr + 190 ms Position Ident. (P3) Pr + 290 ms Position Ident. (P4) Pr + 390 ms Position Ident. (P5) Pr + 490 ms

YEAR AND CONTROL FUNCTIONS (27 BITS) STRAIGHT BINARY SECONDS TIME-OF-DAY CODE (17 DIGITS) Control

Function BIT BIT Time Control

Function

BIT

BIT Time Control Function

BIT

BIT Time SB Code BIT Sub-word Digit Weight

BIT

Time

SB Code

BIT

Subword Digit

Weight

BIT Time

1 Pr + 500 ms Units of Year 01

10 Pr + 600 ms 19 Pr + 700 ms 1 20 = (1) Pr + 800 ms 10 29 = (512) Pr + 900 ms

2 Units of Year 02 11 Pr + 610 ms 20 Pr + 710 ms 2 21 = (2) Pr + 810 ms 11 210 = (1024) Pr + 910 ms

3 Units of Year 04 12 Pr + 620 ms 21 Pr + 720 ms 3 22 = (4) Pr + 820 ms 12 211 = (2048) Pr + 920 ms

4 Units of Year 08 13 Pr + 630 ms 22 Pr + 730 ms 4 23 = (8) Pr + 830 ms 13 212 = (4096) Pr + 930 ms

5 Pr + 540 ms 14 Pr + 640 ms 23 Pr + 740 ms 5 24 = (16) Pr + 840 ms 14 213 = (8192) Pr + 940 ms

6 Tens of Year 10 15 Pr + 650 ms 24 Pr + 750 ms 6 25 = (32) Pr + 850 ms 15 214=(16384) Pr + 950 ms

7 Tens of Year 20 16 Pr + 660 ms 25 Pr + 760 ms 7 26 = (64) Pr + 860 ms 16 215=(32768) Pr + 960 ms

8 Tens of Year 40 17 Pr +…