National Instruments VXI-1394 Getting Started page 47

VXIbus CLK10 Routing
© National Instruments Corporation
When the VXI-1394 is installed in Slot 0 of your mainframe, it supplies
the VXIbus CLK10 signal. The VXI-1394 has four hardware switches that
work together to control various aspects of CLK10 routing. Please read this
section carefully and notice that if you change one switch, you may need to
change another. This section includes several diagrams that show how to
configure the four switches to accomplish various CLK10 configurations.
Conversely, the configuration of one switch may make the setting of
another switch irrelevant. For example, only switches S3 and S4 are
relevant if you install the VXI-1394 in a slot other than Slot 0. The drawings
use the pattern to depict switches that are either irrelevant or disabled
for a particular CLK10 configuration.
Switch S5 uses this pattern in all of the CLK10 drawings. It deals with the
external trigger input SMB and is discussed later in this appendix.
The VXI-1394 can use two different sources to generate the VXIbus
CLK10 signal—an onboard oscillator or the external CLK SMB connector.
Use switch S6 to select between these options. The VXI-1394 uses the
onboard oscillator by default.
The VXI-1394 can also be configured to drive the external CLK SMB from
the VXIbus CLK10 signal. Switch S3 controls whether the VXI-1394
drives or receives the external CLK SMB. If you change the S3 setting to
drive CLK10 out the external CLK10 SMB connector, do not set switch S6
to receive the SMB CLK10 signal; instead use its default setting so that the
onboard oscillator generates the signal.
You can use an additional switch, S4, to control the polarity of the external
CLK SMB signal when S3 is configured to drive it. S4 is unused—its
setting is irrelevant—when S3 is configured to receive the external CLK
SMB signal.
When switch S3 is set so that the VXI-1394 receives the SMB CLK10
signal, you have the option to add a 50 Ω termination to the signal by setting
switch S2. S2 is unused—its setting is irrelevant—when S3 is configured
to drive the external CLK SMB signal.
Appendix C Advanced Hardware Configuration Settings
C-5 VXI-1394 Interface for Windows NT/98