National Instruments VXI-USB User Manual
Appendix C
Advanced Hardware Configuration Settings
© National Instruments Corporation
C-3
When switch S5 is set so that the VXI-USB receives the SMB CLK10
signal, you have the option to add a 50
signal, you have the option to add a 50
Ω termination to the signal by setting
switch S4. S4 is unused when S5 is configured to drive the external CLK
SMB signal.
SMB signal.
Table C-1 summarizes the most common configuration types.
Figure C-2 shows the default settings for the CLK10 switches. This
configuration is as follows:
configuration is as follows:
•
CLK10 is generated from the onboard oscillator (S2).
•
The CLK10 signal is terminated (S4).
•
The VXI-USB receives the external CLK10 signal (S5).
•
The polarity of the CLK10 signal (S6) is irrelevant when the VXI-USB
receives the external CLK10 signal. However, it is configured to be
noninverted when the CLK10 SMB is used as output.
receives the external CLK10 signal. However, it is configured to be
noninverted when the CLK10 SMB is used as output.
Table C-1. Common CLK10 Routing Configurations
Description
Switches
S2 CLK10
Source
S4
Terminate
S5
Direction
S6
Polarity
Generate internal CLK10 with
onboard oscillator
onboard oscillator
ONBRD
N/A
IN
N/A
Generate internal CLK10 and drive
to external CLK SMB
to external CLK SMB
ONBRD
N/A
OUT
NON
Generate internal CLK10 and drive
inverted to external CLK SMB
inverted to external CLK SMB
ONBRD
N/A
OUT
INV
Receive external CLK SMB and
drive to the backplane unterminated
drive to the backplane unterminated
SMB
N
IN
N/A
Receive external CLK SMB with
50
50
Ω termination and drive to the
backplane
SMB
Y
IN
N/A