5700MSC-IP
IP Network Grand Master Clock & Video Master Clock System
Page - 50 Revision 0.2
year 1980. Because the PAL color frame to timecode relationship runs over 4 seconds, this produces
a unique problem when aligning UTC-locked timecode to the PAL color frame.
The system clock of the 5700MSC-IP is always set to UTC time. The PAL reference phase is tied to
GNSS time which is not affected by leap seconds. Whenever a leap second occurs, UTC time counts
an extra second, slowing it down. At the next jam event, the PAL timecode clock could jam to the
system clock causing it to shift backwards by one second. If done this way, it would break the
timecode to color frame relationship. However, the 5700MSC-IP must adjust the time that is jammed
into the 25Hz LTC/VITC clocks in order to maintain color frame alignment. This means is that a static,
positive or negative, 1 or 2 frame offset may be introduced between real time and 25Hz timecode even
when the 5700MSC-IP is locked to GNSS. This static offset will change every time a leap second
occurs.
3.3.5. IRIG Timecode
When equipped with the IRIG option, the 5700MSC-IP is capable of generating IRIG-B timecode from
the LTC outputs and can also read IRIG-B timecode on the LTC input. The IRIG-B formats supported
are shown in Table 3-8. All IRIG-B formats are based on 100-bit timecode that is amplitude modulated
with a 1kHz sine wave carrier. The differences between the four formats are in what additional
information is carried besides the Time-of-Year timestamp. All control flag bits, if present, are set to
zero.
Time-of-Year, Control Flags, Straight Binary Seconds
Time-of-Year, Straight Binary Seconds
Time-of-Year, Year, Control Flags, Straight Binary Seconds
Time-of-Year, Year, Straight Binary Seconds
Table 3-8: Supported IRIG Timecode Formats
The IRIG-B outputs are aligned to the IRIG Datum pulse as shown in Figure 3-20. For an overall view
of the entire IRIG waveform, refer to Figure 3-1. The output waveform consists of a 1kHz carrier that is
amplitude modulated to the IRIG pulse waveform. The frame reference bit (P
R
) leading edge coincides
with the IRIG Datum pulse output from the 5700MSC-IP. When locked to GNSS, IRIG will be aligned
within 20 microseconds of the 1pps pulse from the GNSS receiver (with no global phase offset).
Figure 3-20: Detail of IRIG Alignment to IRIG Datum Pulse
Position Identifier P
0
Reference Bit P
R
IRIG-B12X - Modulated 1kHz Carrier
IRIG1 Datum Pulse
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