National Instruments DAQ X Series, Руководство пользователя

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Chapter 9 Digital Routing and Clock Generation
X Series User Manual 9-4 ni.com
All devices (incl u ding 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 synchrono
u s to the
external reference clock.
Once all of the devices are u sing or referencing a common timebase, yo u
can synchronize operations across them by sending a common start trigger
o
u t across the RTSI or PFI b u s and setting their sample clock rates to the
same val u e.
USB Devices
With the PFI b u s and the ro u ting capabilities of X Series USB devices,
there are several ways to synchronize m u ltiple devices depending on yo u r
application.
To synchronize m u ltiple devices to a common timebase, choose
one device—the initiator—to generate the timebase. The initiator device
ro
u tes its 10 MHz reference clock to one of the PFI <0..15> signals.
All devices (incl u ding 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 synchrono
u s to the external
reference clock.
Once all of the devices are u sing or referencing a common timebase, yo u
can synchronize operations across them by sending a common start trigger
o
u t across the PFI b u s and setting their sample clock rates to the same val u e.
Real-Time System Integration (RTSI)
Real-Time System Integration (RTSI) is a signal b u s among devices that
allows yo u to do the following:
• Use a common clock (or timebase) to drive the timing engine on
m
u ltiple devices
• Share trigger signals between devices
Many National Instr u ments DAQ, motion, vision, and CAN devices
s u pport RTSI.
In a PCI Express system, the RTSI b u s consists of the RTSI b u s interface
and a ribbon cable. The b u s can ro u te timing and trigger signals between
several f u nctions on as many as five DAQ, vision, motion, or CAN devices
in the comp u ter.
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