PXI-665X Datasheet, PDF (2/4 Pages) National Instruments Corporation – PXI and PXI Express Timing and Synchronization Control

PXI and PXI Express Timing and Synchronization Control
Star Trigger Bus
10 MHz
Clock
Local
Bus
132 MB/s, 33 MHz, 32-Bit PCI Bus
PXI Trigger Bus
Figure 4. Diagram of Synchronization Features in the PXI Backplane
Figure 2. Block Diagram of NI PXIe-6672 Master Module
• Star trigger (PXI_STAR) – 13 or 17 equal-trace-length, point-to-point
lines for providing low-skew (<1 ns) trigger or clock signals from slot 2
to slots 3 through 15 in a PXI chassis or the system timing slot to
slots 2 through 17 in a PXI Express chassis.
• Trigger bus (PXI_TRIG) – Eight bused TTL lines for general-purpose
routing of triggers, clocks, and handshaking signals.
• 10 MHz clock (PXI_CLK10) – For improved accuracy, capable devices,
such as the NI PXI-5xxx modular instruments, can phase-lock to this
high-accuracy low-jitter 10 MHz reference clock.
PXI Backplane Overview
PXI-665x and NI PXIe-6672 modules provide full control of the following
timing and synchronization features of the PXI and the PXI Express
backplane, respectively.
CLKIN
AC Coupled
Clock Detector
PFI 0
PFI 1
Driver/
Comparator
PFI 0
Threshold
DAC
Driver/
Comparator
PFI 1
Threshold
DAC
PXI_CLK10_IN
CLOCK and
TRIGGER
Routing
PXI_STAR
<0...12>
PXI_TRIG<0...7>
PCI Interface
To act as a PXI star trigger controller or to provide a high-accuracy
10 MHz reference clock, a PXI-665x module must be installed in slot 2
of the PXI chassis, as shown in Figure 4, and the NI PXIe-6672 must be
installed in the system timing slot of the PXI Express chassis.
High-Stability 10 MHz Timebase
When installed in slot 2 of a PXI chassis, the PXI-6652 and PXI-6653
modules can override the built-in 10 MHz reference clock on a PXI
chassis, and when installed in the system timing slot of a PXI Express
chassis, the NI PXIe-6672 can override the built-in 10 MHz reference
clock on a PXI Express chassis. Typically, most chassis provide a 10 MHz
reference clock with 25 ppm accuracy (10 MHz ±250 Hz). This accuracy is
improved to 1 ppm with the PXI-6652 and NI PXIe-6672, and to 50 ppb
with the PXI-6653. Many modules, such as the PXI-5xxx modular
instruments, have phase-locked-loop (PLL) circuitry to synchronize with
the 10 MHz reference clock.
Figure 3. Block Diagram of PXI-6651 Slave Module
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