© National Instruments
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3-13
PXIe_DSTAR<A..C>
PXI Express devices can provide high-quality and high-frequency point-to-point connections
between each slot and a system timing slot. These connections come in the form of three
low-voltage differential star triggers that route between a PXI Express system timing controller
and a peripheral device. Using multiple connections simplifies the creation of applications
because of the increased routing capabilities.
Table 3-3 describes the three differential star (DSTAR) lines and how they are used.
The DSTAR lines are only available for PXI Express devices when used with a PXI Express
system timing module. For more information, refer to the
PXI Express Specification
at
www.pxisa.org
.
Synchronizing Multiple Devices
On PXI Express systems, you can synchronize devices to PXIe_CLK100. In this application
the PXI Express chassis acts as the master timing source. Each PXI Express module uses
PXIe_CLK100 as its reference clock. Adding channels from multiple modules to the same
NI-DAQmx task will perform synchronization automatically.
Another option in PXI Express systems is to use PXI_STAR. The Star Trigger controller device
acts as the master timing source and drives PXI_STAR with a clock signal. Each target module
uses PXI_STAR as its external reference clock.
Another option in PXI Express Systems is to use PXI_Trig <0..7>. Choose one module to be the
master timebase. The master module routes its 10 MHz RefClk to one of the PXI_Trig <0..7>
signals. All modules (including the master module) then use the 10 MHz RefClk as an external
reference clock source.
Table 3-3.
PXIe_DSTAR Line Descriptions
Trigger Line
Purpose
PXIe_DSTARA
Distributes high-speed, high-quality clock signals from the system
timing slot to the peripherals (input).
PXIe_DSTARB
Distributes high-speed, high-quality trigger signals from the system
timing slot to the peripherals (input).
PXIe_DSTARC
Sends high-speed, high-quality trigger or clock signals from the
peripherals to the system timing slot (output).
