Safran SecureSync 2400 User Manual page 615

Figure 5-68: FAA modified IRIG B
Notes
The beginning of each 1.0 second time frame is identified by two consecutive
8.0 ms elements (P
(P ) is the "on time" reference point for the succeeding time code. 10 pps pos-
R
ition identifiers P
and refer to the leading edge of the succeeding element.
The time code word and the control functions presented during the time frame
are pulse-width coded. The binary "zero" and index markers have a duration of
2.0 ms, and the binary "one" has a duration of 5.0 ms. The leading edge is the
100 pps "on time" reference point for all elements.
The binary coded decimal (BCD) time-of-year code word consists of 30 digits
beginning at index count 1. The binary coded subword elements occur between
position identifiers P
days) until the code word is complete. An index marker occurs between the
decimal digits in each subword to provide separation for visual resolution. The
least significant digit occurs first. The BCD code recycles yearly.
Twenty- seven control functions occur between position identifiers P
FAA uses this field to communicate satellite lock status and time error and indic-
ators. The first flag element is at 530 ms which indicates satellite lock. The ±1ms
error flag occurs at 550 ms. The ±5ms error flag occurs at 560 ms. The ±50 ms
error flag occurs at 570 ms. The ±500 ms error flag occurs at 580 ms.
SecureSync 2400 User Manual
and P ). The leading edge of the second 8.0 ms element
0 8
, P , ..... P (8.0 ms duration) occur 10 ms before 10 pps "on time"
0 1 8
and P (7 for seconds; 7 for minutes; 6 for hours; 10 for
0 5
APPENDIX
and P .
5 8
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