Chapter 1
Getting Started
NI PXI-1042 Series User Manual
1-8
ni.com
Figure 1-4.
PXI Local Bus and Star Trigger Routing
Trigger Bus
All slots share eight trigger lines. You can use these trigger lines in a variety
of ways. For example, you can use triggers to synchronize the operation of
several different PXI peripheral modules. In other applications, one module
can control carefully timed sequences of operations performed on other
modules in the system. Modules can pass triggers to one another, allowing
precisely timed responses to asynchronous external events the system is
monitoring or controlling.
System Reference Clock
The PXI-1042 Series chassis supply the PXI 10 MHz system clock signal
(PXI_CLK10) independently to each peripheral slot. An independent
buffer (having a source impedance matched to the backplane and a skew of
less than 250 ps between slots) drives the clock signal to each peripheral
slot. You can use this common reference clock signal to synchronize
multiple modules in a measurement or control system. You can drive
PXI_CLK10 from an external source through the PXI_CLK10_IN pin
on the P2 connector of the Star Trigger Slot. Refer to Table B-4,
Connector Pinout for the Star Trigger Slot
. Sourcing an external clock on
this pin automatically replaces the backplane’s 10 MHz source. You also
can drive PXI_CLK10 from the 10 MHz REF IN connector on the rear of
the chassis. Sourcing an external clock on this connector automatically
Star Triggers
PCI Arbitration and Clock Signals
System Controller Slot [1]
Local
Bus
Star Trigger/Peripheral Slot [2]
Peripheral Slot [3]
Peripheral Slot [4]
Peripheral Slot [7]
Peripheral Slot [8]
Local
Bus
Local
Bus
