Chapter 4
Synchronization
NI PXI-6682 User Manual
4-2
ni.com
instrument uses to synchronize its timebase to the IRIG source. The rest of
the data contains information such as the time of day, days since the
beginning of the year, and optionally, control functions and the number of
seconds since the start of the day, encoded as a straight binary number.
Refer to Appendix B,
IRIG Protocol Overview
, for more information about
the IRIG standard.
The NI PXI-6682 can function as an IRIG-B receiver, supporting
synchronization to sources outputting IRIG-B 12X (AM) and
IRIG-B 00X (DC).
When configured to synchronize to an IRIG-B AM source, the NI
PXI-6682 will be able to accept a 1kHz AM modulated IRIG-B 12X signal
on its PFI0 input. When configured to synchronize to an IRIG-B DC
source, the NI PXI-6682 will be able to accept an IRIG-B 00X DC encoded
signal on its PFI0 input.
Caution
Do not connect an AM signal to PFI0 when the PFI line is configured for digital
operations. This could cause damage to the digital circuitry, the device driving the AM
signal, or both. Always ensure the line is configured for IRIG-B AM operation before
connecting an IRIG-B AM signal.
Furthermore, once the NI PXI-6682 is synchronized to IRIG-B, it can
function as an IEEE 1588 grandmaster to synchronize of external 1588
devices.
The following assumptions are made regarding the received IRIG-B signal.
All conditions must be met for the NI PXI-6682 to be able to synchronize
accurately:
•
Seconds begin every minute at 0, increment to 59, and then roll-over
to 0.
•
Minutes begin every hour at 0, increment to 59, and then roll-over to 0.
•
Hours begin every day at 0, increment to 23, and then roll-over to 0.
•
Days begin every year at 1. Days increment to 365 in non-leap years,
or to 366 in leap years, and then roll-over to 1. Leap years must be
supported. Valid values for year are 01–99, inclusive. Years are
assumed to be in the XXI Century. For instance, year
07
represents
2007. If the year is not supplied (sent as
00
), the OS system time is
read and the year is derived from it.
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