GPS, IEEE 1588, and IRIG-B Timing and Synchronization Modules for PXI and PXI Express
Synchronize PXI and PXI Express Systems
Using GPS, IEEE 1588, or IRIG-B
With the PXI-6682 and PXI-6682H, you can use GPS, IEEE 1588, IRIG-B, or PPS
signals as the time reference to synchronize with other devices or PXI and
PXI Express systems. You have not only a synchronized clock for multiple PXI
and PXI Express systems but also a common time reference. Because of this,
you can generate synchronized future time events and timestamp incoming
signals with the synchronized time.
The GPS receiver on the PXI-6682 and PXI-6682H can power an active GPS
antenna and receive and process the RF signals (1.575 GHz) from satellites. It
generates a very precise pulse-per-second (PPS) signal that the PXI-6682 and
PXI-6682H use to achieve submicrosecond synchronization. Because of this,
Figure 2. Functional Overview of the PXI-6682
you can use the PXI-6682 and PXI-6682H to synchronize spatially located PXI
and PXI Express systems as long as GPS satellites are visible to the antenna
from those locations. Furthermore, once the PXI-6682 and PXI-6682H are
synchronized to GPS, they can function as IEEE 1588 grandmasters to achieve
synchronization of external 1588 devices. NI-Sync 3.1 or later supports
IEEE 1588-2008. NI-Sync 3.0 is available on the Web for those who need
IEEE 1588-2002 support.
Note: The PXI-6682H does not have PXI_STAR trigger lines, shown as
PXI_STAR<0..12> in Figure 2. The PXI-6682H does not have the CLKIN circuitry
or the ability to drive PXI_CLK10_IN.
Star Trigger Bus
10 MHz
Clock
PXI-6682 as a Star Trigger Controller
The PXI-6682 provides full control of the timing and synchronization features
of the PXI backplane (Figure 3). To act as a PXI star trigger controller or to offer
a high-accuracy, free-running 10 MHz reference clock, the PXI-6682 must be
installed in slot 2 of the PXI chassis, as shown in Figure 1. It is capable of routing
signals to and from the front panel, the PXI star triggers, and the PXI triggers.
In addition, you can invert the polarity of the destination signal, which is useful
when handling active-low digital signals. The PXI-6682 can also route a 10 MHz
clock from CLKIN to the PXI 10 MHz reference clock and route the TCXO or PXI
10 MHz reference clock to CLKOUT. Refer to Figure 2 for the PXI-6682 functional
block diagram.
Local
Bus
132 MB/s, 33 MHz, 32-Bit PCI Bus
PXI Trigger Bus
Figure 3. Diagram of Synchronization Features in the PXI Backplane
Synchronizing PXI Express Systems
with the PXI-6682H
You can use the PXI-6682H in any PXI hybrid-compatible slot in PXI Express
chassis with PXI hybrid slots. By using the PXI-6682H in such a system, you
can timestamp events and create future time events on the PXI_TRIG lines as
well as reference your system time to GPS, IEEE 1588, or IRIG-B. The PXI-6682H
is essentially the same module as the PXI-6682 except NI has removed one
connector so the PXI-6682H can plug into PXI Express systems. For this reason,
you cannot drive PXI_CLK10, the PXI_STAR trigger lines, or any of the PXI
Express clocks and triggers. If you wish to override CLK_10 in a PXI Express
system, you can route a coaxial cable from CLKOUT on the PXI-6682H to the
10 MHz clock input on the rear of the PXI Express chassis (if the chassis you
have selected has this input). To drive the PXI_STAR trigger lines, you must also
incorporate a PXI Express timing module such as the NI PXIe-6672.
Figure 1. The PXI-6682 is connected to an active GPS antenna and installed in a system
timing slot (slot 2) of an NI PXI-1042 chassis.
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