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Chapter 3
Acquiring Analog Input
PXIe_SYNC100
PXIe_SYNC100 is a common, low-skew 10 MHz reference clock with a 10% duty cycle for
synchronization of multiple modules in a PXI Express measurement or control system. The
PXI Express backplane is responsible for generating PXIe_SYNC100 independently to each
peripheral slot in a PXI Express chassis. PXIe_SYNC100 allows modules using PXIe_CLK100
as their reference to recreate the timing of the PXI_CLK10 signal while taking advantage of the
lower skew of PXIe_CLK100. For more information, refer to the
PXI Express Specification
at
www.pxisa.org
.
PXI_CLK10
PXI_CLK10 is a common, low-skew 10 MHz reference clock for synchronization of multiple
modules in a PXI measurement or control system. The PXI backplane is responsible for
generating PXI_CLK10 independently to each peripheral slot in a PXI chassis. In PXI Express
chassis, the PXI_CLK10 signal is in phase with PXIe_CLK100.
Note
PXI_CLK10 cannot be used as a reference clock for SC Express modules.
PXI Triggers
A PXI/PXI Express chassis provides eight bused trigger lines to each module in a system.
Triggers may be passed from one module to another, allowing precisely timed responses to
asynchronous external events that are being monitored or controlled. Triggers can be used to
synchronize the operation of several different PXI peripheral modules.
In a PXI chassis with more than eight slots, the PXI trigger lines may be divided into multiple
independent buses. Refer to the documentation for your chassis for details.
PXI_STAR Trigger
In a PXI Express system, the Star Trigger bus implements a dedicated trigger line between the
system timing slot and the other peripheral slots. The Star Trigger can be used to synchronize
multiple modules or to share a common trigger signal among modules.
A system timing controller can be installed in the system timing slot to provide trigger signals
to other peripheral modules. Systems that do not require this functionality can install any
standard peripheral module in this system timing slot.
An SC Express module receives the Star Trigger signal (PXI_STAR) from a System timing
controller. PXI_STAR can be used as a trigger signal for input operations.
An SC Express module is not a system timing controller. An SC Express module can be used in
the system timing slot of a PXI system, but the system will not be able to use the Star Trigger
feature.
