National Instruments Isolated Analog Input Device NI PXI-4224 - Manual (Page 34)

Chapter 4 Theory of Operation
© National Instruments Corporation 4-7 NI PXI-4224 User Manual
Device and PXI Clocks
Many functions performed by the NI PXI-4224 require a frequency
timebase to generate the necessary timing signals for controlling
A/D conversions, digital-to-analog converter (DAC) updates, or
general-purpose signals at the I/O connector.
The NI PXI-4224 can use either its internal 20 MHz master timebase or a
timebase received over the PXI trigger bus on the PXI clock line. These
timebases are software configurable. If you configure the device to use the
internal timebase, you can program the device to drive its internal timebase
over the PXI trigger bus to another device programmed to receive this
timebase signal. This clock source, whether local or from the PXI trigger
bus, is used directly by the device as the primary frequency source. The
default configuration is to use the internal timebase without driving the PXI
trigger bus timebase signal. The NI PXI-4224 can use the PXI_Trig<7>
line to synchronize
Master Timebase with other devices.
For the NI PXI-4224, PXI Trig<0..5>, and PXI_Star, connect through the
NI PXI-4224 backplane. The PXI Star Trigger line allows the NI PXI-4224
to receive triggers from any Star Trigger controller plugged into slot 2 of
the chassis. For more information about the Star Trigger, refer to the
PXI Hardware Specification, Revision 2.1 and PXI Software Specification,
Revision 2.1.