Meinberg TCR511 - Manual (Page 5)

5
Introduction
The transmission of coded timing signals began to take on widespread importance in
the early 1950´s. 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
definition of time code formats was completely arbitrary and left to the individual ideas of
each design engineer. Hundreds of different time codes were formed, some of which
were standardized by the „Inter Range Instrumantation Group“ (IRIG) in the early 60´s.
Except these „IRIG Time Codes“ other formats, like NASA36, XR3 or 2137, are still
in use. The board TCR511 however only decodes IRIG-A, IRIG-B or AFNOR NFS
87-500 formats. The AFNOR code is a variant of the IRIG-B format. Within this code
the complete date is transmitted instead of the ‘Control Functions’ of the IRIG-telegram.
Description of IRIG-Codes
The specification of individual IRIG time code formats is defined in IRIG Standard 200-
98. They are described by an alphabetical character followed by a three-digit number
sequence. The following identification is taken from the IRIG Standard 200-98 (only the
codes relevant to TCR511 are listed):
character bit rate designation A 1000 pps
B 100 pps
1st digit form designation 0 DC Level Shift
width coded
1 sine wave carrier
amplitude modulated
2nd digit carrier resolution 0 no carrier (DC Level Shift)
1 100 Hz, 10 msec resolution
2 1 kHz, 1 msec resolution
3 10 kHz, 100
µsec resolution
3rd digit coded expressions 0 BCD, CF, SBS
1 BCD, CF
2 BCD
3 BCD, SBS
BCD: time of year, BCD-coded
CF: Control-Functions (user defined)
SBS: seconds of day since midnight (binary)