FAA IRIG B OUTPUT
The FAA IRIG B code contains the Binary Coded Decimal (BCD) time of year and
a Control Function (CF) field containing satellite lock status and time error flags.
With the exception of the position identifiers, all remaining code elements are set
to a binary 0. Figure A-1 illustrates the FAA IRIG B data structure. The BCD time
of year provides the day of the year, 001-366, and the time of day including
seconds. The hour of the day is expressed in 24-hour format.
FAA IRIG B General Description
1. Time frame: 1.0 seconds
2. Pulse rates:
A. Element rate: 100 per second
B. Position identifier rate: 10 per second
C. Reference marker rate: 1 per second
3. Element identification: The "on time" reference point for all elements is the
pulse leading edge.
A. Index marker (Binary 0 or uncoded element): 2 millisecond duration
B. Code digit (Binary 1): 5 millisecond duration
C. Position identifier: 8 millisecond duration
D. Reference marker, 1 per second. The reference marker appears as two
consecutive position identifiers. The second position identifier marks
the on-time point for the succeeding code word.
4. Resolution: 10 milliseconds
5. Code word structure:
BCD: Word seconds digits begin at index count 1. Binary coded ele-
ments occur between position identifier elements P0 and P5 (7 for
seconds, 7 for minutes, 6 for hours, and 10 for days) until the code
word is complete. An index marker occurs between decimal digits in
each group to provide separation for visual resolution. Least sig-
nificant digit occurs first.
CF: IRIG formats reserve a set of elements known as Control Func-
tions (CF) for the encoding of various control, identification, or other
special purpose functions. IRIG B has 27 Control Functions located
SecureSync 2400 User Manual 597
APPENDIX
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