Usb Devices; Real-Time System Integration (Rtsi) - National Instruments DAQ X Series User Manual

Chapter 9 Digital Routing and Clock Generation
All devices (including the initiator device) receive the 10 MHz reference
clock from RTSI or PFI. This signal becomes the external reference clock.
A PLL on each device generates the internal timebases synchronous to the
external reference clock.
Once all of the devices are using or referencing a common timebase, you
can synchronize operations across them by sending a common start trigger
out across the RTSI or PFI bus and setting their sample clock rates to the
same value.

USB Devices

With the PFI bus and the routing capabilities of X Series USB devices,
there are several ways to synchronize multiple devices depending on your
application.
To synchronize multiple devices to a common timebase, choose
one device—the initiator—to generate the timebase. The initiator device
routes its 10 MHz reference clock to one of the PFI <0..15> signals.
All devices (including the initiator device) receive the 10 MHz reference
clock from PFI. This signal becomes the external reference clock. A PLL
on each device generates the internal timebases synchronous to the external
reference clock.
Once all of the devices are using or referencing a common timebase, you
can synchronize operations across them by sending a common start trigger
out across the PFI bus and setting their sample clock rates to the same value.

Real-Time System Integration (RTSI)

Real-Time System Integration (RTSI) is a signal bus among devices that
allows you to do the following:
•
•
Many National Instruments DAQ, motion, vision, and CAN devices
support RTSI.
In a PCI Express system, the RTSI bus consists of the RTSI bus interface
and a ribbon cable. The bus can route timing and trigger signals between
several functions on as many as five DAQ, vision, motion, or CAN devices
in the computer.
X Series User Manual
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Use a common clock (or timebase) to drive the timing engine on
multiple devices
Share trigger signals between devices
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