National Instruments VXI-1394 - Manual (Page 47)

Appendix C Advanced Hardware Configuration Settings
VXI-1394 User Manual for Windows C-6 ni.com
VXIbus CLK10 Routing
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. 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.
Notice that the configuration of one switch may make the setting of another
switch irrelevant. For example, only switches S2 and S3 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 S4 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 S5 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 S2 controls whether the VXI-1394
drives or receives the external CLK SMB. If you change the S2 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, S3, to control the polarity of the external
CLK SMB signal when S2 is configured to drive it. S3 is unused when S2
is configured to receive the external CLK SMB signal.
When switch S2 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 S1. S1 is unused when S2 is configured to drive the external CLK
SMB signal.