National Instruments MXI Getting Started page 48

Appendix B Common Questions
What do the LEDs on the front of the VXI-MXI-2 or VME-MXI-2
mean?
The SYSFAIL LED shows the state of the VXIbus/VMEbus SYSFAIL
line. This line is asserted whenever any device in the chassis has not yet
passed its self test, if it has failed its self test, or if it has detected a failure
after originally passing its self test. The MXI LED indicates that the
VXI-MXI-2 or VME-MXI-2 is acting as a slave to another device on the
MXIbus, such as when the PCI-MXI-2 or PXI-8320 communicates with
either the VXI-MXI-2 or VME-MXI-2 or with another device in the
chassis. The VXI (VME) LED, when lit, indicates that the VXI-MXI-2 or
VME-MXI-2 is acting as a slave to another device in the VXI (VME)
chassis, such as when a bus master inside the chassis wants to talk to either
the VXI-MXI-2 or VME-MXI-2 or another device outside the chassis.
Are the VXI-MXI-2 and either the PCI-MXI-2 or PXI-8320 two
devices or one with respect to the VXIbus?
The PCI-MXI-2, PXI-8320, and the VXI-MXI-2 are unique VXIbus
devices with their own logical addresses. However, the MXIbus allows the
PCI or PXI/CompactPCI computer to behave as if it is inside the chassis
with the VXI-MXI-2 by transparently converting PCI bus cycles to MXIbus
cycles to VXIbus cycles, and vice versa.
I have a system that requires rugged chassis and bulkhead cables.
Can I still use MXIbus?
Yes, National Instruments sells MXIbus bulkhead cables. Contact National
Instruments for further information.
What kind of signal is CLK10 and what kind of signal do I need for an
external CLK10?
CLK10 is a differential ECL signal on the VXIbus backplane. However, the
oscillator for the VXI-MXI-2 and the EXTCLK input from the front panel
use TTL. Therefore, supply a TTL-level signal for EXTCLK; our voltage
converters will convert the signal to differential ECL.
CLK10 is not applicable to VME.
What is the accuracy of the CLK10 signal?
The CLK10 generated by the VXI-MXI-2 is 100 ppm (0.01%) as per the
VXIbus specification. If you need a more accurate CLK10 signal, you can
use the EXTCLK input at the front of the VXI-MXI-2.
CLK10 is not applicable to VME.
© National Instruments Corporation B-7 PCI-Based MXI-2 Interfaces for Windows 2000/NT/Me/98