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National Instruments Corporation
B-1
NI PXI-6682 User Manual
B
IRIG Protocol Overview
IRIG (Inter Range Instrumentation Group) is a standard used to transmit
precise timing information between instruments to achieve
synchronization. There are 6 different IRIG standards defined (A,B,D,E,G
and H). The main difference between the standards is the rate with which
the synchronization pulses and the information bits are sent. The standards
also differ slightly in the content of the information transmitted. Table B-1
summarizes the characteristics of each IRIG standard
In addition to the characteristics of each standard described in the table
above, each of those is subdivided further depending on the electrical
characteristics of the signal used to transmit the data, and the actual data
Table B-1.
IRIG Standard Definitions
IRIG Standard
Bit rate (bit
duration)
Frame rate (frame
duration)
Information sent
IRIG-A
1 Kbps (1ms)
10 fps (100ms)
TOY & Y (BCD)
SOD (SBS)
IRIG-B
100 bps (10ms)
1 fps (1s)
TOY & Y (BCD)
SOD (SBS)
IRIG-D
1 bpm (60s)
1 fpm (1 hour)
TOY (BCD)
days and hours only
IRIG-E
10 bps (100ms)
6 fpm (10s)
TOY & Y (BCD)
IRIG-G
10 kbps (0.1ms)
100 fps (10ms)
TOY & Y (BCD)
Includes fractions of
seconds
IRIG-H
1 bps (1s)
1fpm (60s)
TOY (BCD)
Days, hours and
minutes only
bps—bits per second
fps—frames per second
TOY—time of year
SOD—seconds of day
bpm—bits per minute
fpm—frames per minute
Y—year
SBS—straight binary seconds
BCD—binary-coded decimal
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