National Instruments NI 6120 - Manual (Page 13)

Chapter 1 Introduction
NI 6115/6120 User Manual 1-2 ni.com
you do not need the RTSI cable for system triggering and timing on the
PXI. In addition, a phase-locked loop (PLL) circuit accomplishes the
synchronization of multiple NI PXI-6115/6120 devices or other PXI
devices which support PLL synchronization by allowing these devices to
all lock to the same reference clock present on the PXI backplane. Refer to
the
Phase-Locked Loop Circuit section of Chapter 3, Hardware Overview ,
for more information.
Detailed specifications of the NI 6115/6120 are in Appendix A,
Specifications .
Using PXI with CompactPCI
The ability to use PXI-compatible products with standard CompactPCI
products is an important feature of PXI Specification Revision 2.0. If you
use a PXI-compatible plug-in device in a standard CompactPCI chassis,
you are unable to use PXI-specific functions, but you can still use the basic
plug-in device functions. For example, the RTSI interface on the
NI PXI-6115/6120 is available in a PXI chassis, but not in a CompactPCI
chassis.
The CompactPCI specification permits vendors to develop sub-buses that
coexist with the basic PCI interface on the CompactPCI bus. Compatible
operation is not guaranteed between CompactPCI devices with different
sub-buses nor between CompactPCI devices with sub-buses and PXI
devices. The standard implementation for CompactPCI does not include
these sub-buses. The NI PXI-6115/6120 works in any standard
CompactPCI chassis adhering to PICMG CompactPCI 2.0 R3.0.
PXI-specific features are implemented on the J2 connector of the
CompactPCI bus. Table 1-1 lists the J2 pins used by the NI PXI-6115/6120.
The PXI device is compatible with any CompactPCI chassis with a sub-bus
that does not drive these lines. Even if the sub-bus is capable of driving
these lines, the PXI device is still compatible as long as those pins on the
sub-bus are disabled by default and are never enabled.
Caution Damage can result if these lines are driven by the sub-bus.