Chapter 3
Integration and System Considerations
NI PXIe-5450 User Manual
3-6
ni.com
System Reference Clock, PXI_CLK10
The PXI chassis supplies the PXI 10 MHz system Reference clock signal
(PXI_CLK10) independently to each peripheral slot. An independent
buffer drives the clock signal to each peripheral slot. The buffer has a
source impedance matched to the backplane and a skew ranging from less
than 1 ns to better than 250 ps between slots. You can use this common
Reference clock signal to synchronize multiple devices in a measurement
or control system. You can drive PXI_CLK10 from an external source
through the PXI_CLK10_IN pin on the P2 connector of the PXI star trigger
slot, which is slot 2. Sourcing an external clock on this pin automatically
disables the 10 MHz source on the backplane. You can synchronize
multiple chassis that have connectors on the back panel for 10 MHz
reference in and 10 MHz reference out. Refer to your PXI chassis
documentation for more information.
PFI Lines
PFI lines are multipurpose programmable function input/outputs. These
lines serve as connections to virtually all internal timing signals. NI signal
generators have up to six digital lines that can accept or generate a trigger,
generate a marker, accept or generate a Reference clock. The function of
each PFI line is independent.
If you are using LabVIEW to program your signal generator and you want
to connect external signal generators to the PFI lines, you can use the
niFgen Configure Sample Clock Source VI, the niFgen Configure
Reference Clock VI, or the niFgen Configure Trigger VI to route external
signals to internal sources. You can use the niFgen Export Signal VI to
route internal signals to the PFI lines on the front panel.
If you are using LabWindows/CVI to program your signal generator, you
can use the
niFgen_ConfigureSampleClockSource
function, the
niFgen_ConfigureReferenceClock
function, or the
niFgen_ConfigureTriggerSource
function to route external signals to
internal sources. You can use the
niFgen_ExportSignal
function to
route internal signals to the PFI lines on the front panel.
Caution
If you enable a PFI line for output, do
not
connect any external signal source to
it; doing so can damage the device, the computer, and the connected equipment.
