54 Timing, IRIG-B and Pulses
Figure 7.2: IRIG-B Waveforms
7.3.3 IRIG-B IEEE 1344 Extension
As mentioned above, the IEEE 1344 enables extra bits of the Control Function (CF) portion of the
IRIG-B time code. Within this portion of the time code, bits are designated for additional features,
including:
• Calendar Year (old method, now called BCD
Y EAR
)
• Leap seconds, and leap seconds pending
• Daylight saving time (DST), and DST pending
• Local time offset
• Time quality
• Parity
• Position identifiers
To be able to use these extra bits of information, protective relays, RTU’s and other equipment
receiving the time code must be able to decode them. Consult your equipment manual to determine
if the IEEE 1344 feature should be turned ON in the clock. To view details of the IEEE Std 1344-
1995, please check with the IEEE.
NOTE: To download a copy of of the IRIG-B 2004 specification, please use the link to the Arbiter
web site.
http://arbiter.com/resources/documentation.php and select Timing and Frequency, then select Ap-
plication Notes/Option Information.
7.3.4 1 Pulse-per-Second (1 PPS)
A one pulse-per-second timing output signal is very simple in concept. It is a digital bit transmitted
every second with a pulse width of 10 milliseconds. Probably the most critical part of this signal is
that the rising edge is “on time” as compared with the signal from the Global Positioning System
(GPS). When configured from any of the TTL/CMOS (5-volt) drivers, it has the same drive power
as the IRIG-B and the Programmable Pulse. See Figure 7.2 for a comparison between unmodulated
IRIG-B and 1 PPS.
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