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Page 14 7 Time codes
7 Time codes
The transmission of coded timing signals began to take on widespread importance in the early 1950s. Especially
the US missile and space programs were the forces behind the development of these time codes, which were used
for the correlation of data. The denition of time code formats was completely arbitrary and left to the individual
ideas of each design engineer. Hundreds of dierent time codes were formed, some of which were standardized
by the Inter Range Instrumentation Group (IRIG) in the early 60s.
Except these IRIG Time Codes other formats, like NASA36, XR3 or 2137, are still in use. The board PTP270PEX
however generates the IRIG-B, AFNOR NFS 87-500 code as well as IEEE1344 code which is an IRIG-B123 coded
extended by information for time zone, leap second and date. If desired other formats are available.
7.1 The time code generator
The board PTP270PEX generates unmodulated timecodes which are transmitted by modulating the pulse dura-
tion of a DC-signal (TTL in case of PTP270PEX), see chapter IRIG standard format for details.
Transmission of the time code is synchronized to the PPS (pulse per second) derived from synchronization
to the IEEE 1588 grandmaster.
The modulated pulses have the following durations:
a) binary 0 : 2 msec
b) binary 1 : 5 msec
c) position-identier : 8 msec
7.2 Generated Time Codes
The board PTP270PEX is capable of generating the following unmodulated timecodes:
a) B002: 100 pps, DCLS signal, no carrier
BCD time-of-year
c) B003: 100 pps, DCLS signal, no carrier
BCD time-of-year, SBS time-of-day
e) AFNOR: Code according to NFS-87500, 100 pps, wave signal,
1kHz carrier frequency, BCD time-of-year, complete date,
SBS time-of-day, Signal level according to NFS-87500
f) IEEE1344: Code according to IEEE1344-1995, 100 pps, AM sine wave signal,
1kHz carrier frequency, BCD time-of-year, SBS time-of-day,
IEEE1344 extensions for date, timezone, daylight saving and
leap second in control functions (CF) segment.
(also see table 'Assignment of CF segment in IEEE1344 mode')
14 Date: 22nd November 2012 PTP270PEX