National Instruments Multifunction RIO NI R Series, User Manual

Page: 39 / 71

Chapter 2 Hardware Overview of the NI 78xxR
R Series Multifunction RIO User Manual 2-20 ni.com
The SHC68-68-RDIO was designed specifically for R Series devices and is
the NI-recommended cable for digital applications. If yo
u
are
u
sing the
SH68-C68-S cable, however, please note the following considerations.
The SH68-C68-S shielded cable contains 34 twisted pairs of cond
u
ctors. To
maximize the digital I/O available on the NI 78 xx R, some of the DIO lines
are twisted with power or gro
u
nd and some DIO lines are twisted with other
DIO lines. To obtain maxim
u
m signal integrity, place edge-sensitive or
high-freq
u
ency digital signals on the DIO lines that are paired with power
or gro
u
nd. Beca
u
se the DIO lines that are twisted with other DIO lines can
co
u
ple noise onto each other,
u
se these lines for static signals or
non-edge-sensitive, low-freq
u
ency digital signals. Examples of
high-freq
u
ency or edge-sensitive signals incl
u
de clock, trigger, p
u
lse-width
mod
u
lation (PWM), encoder, and co
u
nter signals. Examples of static
signals or non-edge-sensitive, low-freq
u
ency signals incl
u
de LEDs,
switches, and relays. Table 2-4 s
u
mmarizes these g
u
idelines.
Table 2-4. DIO Signal Guidelines for the NI 78 xx R
Device Digital Lines
SH68-C68-S
Shielded Cable
Signal Pairing
Recommended Types
of Digital Signals
NI 781 x R DIO<0..27> DIO line paired
with power
or gro
u
nd
All types—high-freq
u
ency or
low-freq
u
ency signals,
edge-sensitive or
non-edge-sensitive signals
DIO<28..39> DIO line paired
with another
DIO line Static signals or
non-edge-sensitive,
low-freq
u
ency signals
NI 783 x R,
NI 784 x R,
NI 785 x R
Connector 0, DIO<0..7>;
Connector 1, DIO<0..27>;
Connector 2, DIO<0..27> DIO line paired
with power
or gro
u
nd
All types—high-freq
u
ency or
low-freq
u
ency signals,
edge-sensitive or
non-edge-sensitive signals
Connector 0, DIO<8..15>;
Connector 1, DIO<28..39>;
Connector 2, DIO<28..39> DIO line paired
with another
DIO line Static signals or
non-edge-sensitive,
low-freq
u
ency signals