Chapter 3
Signal Connections
©
National Instruments
3-19
NI 660x User Manual
Inductive Effects
For high-speed signals, ind
u
ctive effects can degrade signal integrity and
ca
u
se ringing. To minimize ind
u
ctive effects, yo
u
m
u
st minimize gro
u
nd
loops and allow a ret
u
rn path for c
u
rrents. Twist yo
u
r signal with a gro
u
nd
wire when yo
u
connect it to the 68-pin connector block yo
u
are
u
sing.
Connect the signal wire to the PFI pin yo
u
are
u
sing and connect the gro
u
nd
wire to the adjacent D GND line with which the PFI line is twisted.
Fig
u
re 3-11 shows an example of wiring that minimizes ind
u
ctive effects.
Figure 3-11.
Example of Wiring That Minimizes Inductive Effects
The SH68-68-D1 cable is designed to help minimize ind
u
ctive effects.
Each signal line is twisted with a gro
u
nd wire connected to a nearby pin.
Each gro
u
nd wire is shared by two signal lines.
Table 3-8 lists the signals and the D GND pin n
u
mber on the 68-pin
connector block.
Table 3-8.
Signals and D GND Pin Number on 68-Pin Connector Block
PFI Number
Pin Number for D GND
PFI 0
11
PFI 1
PFI 2
46
PFI 3
PFI 4
14
PFI 5
PFI 6
49
PFI 7
PFI 8
50
PFI 9
PFI 39 Pin 2
GND Pin 36
GND
Output of External Device
SCB-68
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