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SC Express Considerations
This chapter details the clock and trigger functionality available through the PXI Express
chassis.
SC Express Clock and Trigger Signals
PXIe_CLK100
PXIe_CLK100 is a common, low-skew 100 MHz reference clock used for synchronization of
multiple modules in a PXI Express measurement or control system. The PXIe backplane is
responsible for generating PXIe_CLK100 independently to each peripheral slot in a PXI Express
chassis. For more information, refer to the
PXI Express Specification
at
www.pxisa.org
.
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 PXIe 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/PXIe 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.
