Chapter 2 Hardware Overview ofthe NI PXI-7831R
NI PXI-7831R User Manual 2-18 ni.com
edge-sensitive or high-frequency digital signals on the DIO lines that are
paired with power or ground. Because the DIO lines that are twisted with
other DIO lines can couple noise onto each other, these lines should be used
for static signals or for non-edge-sensitive, low-frequency digital signals.
Examples of high-frequency or edge-sensitive signals include clock,
trigger, pulse-width modulation (PWM), encoder, and counter signals.
Examples of static signals or non-edge-sensitive, low-frequency signals
include LEDs, switches, and relays. Table2-4 summarizes these
guidelines.
PXI Trigger Bus
The NIPXI-7831R can send and receive triggers throug h the PXI trigger
bus, which provides eight trigger lines that link all PXI slots in a bus
segment. These trigger lines connect to the FPGA on the NI PXI-7831R
and can be used just like any of the other NIPX I-7831R DIO lines.
The PXI trigger lines can be used to synchronize an NI PXI-7831R to any
other device that supports PXI triggers. The PXI trigger lines on the
NIPXI-78 31R are PXI/TRIG<0..7>. In addition, the NI PXI-7831R can
use the PXI star trigger line to send or receive triggers from a device
plugged into slot 2 of the PXI chassis. The PXI star trigger line on the
NIPXI-78 31R is PXI/STAR.
The PXI-7831R can configure each PXI trigger line either as an input or an
output signal. Since each PXI trigger line in the PXI trigger bus is
connected in parallel to all the PXI slots in a bus segment, only one PXI
device can drive a particular PXI trigger line at a time. For example, if one
NIPXI-78 31R is configured to send out a trigger pulse on PXI/TRIG<0>,
the remaining devices on that PXI bus segment must have PXI/TRIG<0>
configured as an input.
Table 2-4. DIO Signal Guidelines for the NIPXI-7831R
Digital Lines
SH68-C68-S Shielded Cable
Signal Pairing
Recommended Types
ofDi gital Signals
Connector 0, DIO<0..7>;
Connector 1, DIO<0..27>;
Connector 2, DIO<0..27>
DIO line paired with power
orground
All types (high frequency or low
frequency 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-frequency signals