National Instruments NI 781xR - Manual (Page 20)

Chapter 2 Hardware Overview of the NI 781xR
NI 781xR User Manual 2-2 ni.com
NI 7811R Overview
The NI 7811R has 160 bidirectional DIO lines and a one million gate
FPGA.
NI 7813R Overview
The NI 7813R has 160 bidirectional DIO lines and a three million gate
FPGA.
Digital I/O
You can configure the NI 781xR DIO lines individually for either input or
output. When the system powers on, the DIO lines are all high-impedance.
To set another power-on state, you can configure the NI 781xR to load a VI
when the system powers on. This VI then can then set the DIO lines to any
power-on state.
Connecting Digital I/O Signals
The DIO signals on the NI 781xR connectors are DGND and DIO<0..39>.
DIO<0..n> signals make up the DIO port, and DGND is the ground
reference signal for the DIO port. The NI 781xR has four DIO connectors
for a total of 160 DIO lines.
Refer to Figure B-1, NI 781xR Connector Locations , and Figure B-2,
NI 781xR I/O Connector Pin Assignments , for the connector locations and
the I/O connector pin assignments on the NI 781xR.
The DIO lines on the NI 781xR are TTL compatible. When configured as
inputs, they can receive signals from 5 V TTL, 3.3 V LVTTL, 5 V CMOS,
and 3.3 V LVCMOS devices. When configured as outputs, they can send
signals to 5 V TTL, 3.3 V LVTTL, and 3.3 V LVCMOS devices. Because
the digital outputs provide a nominal output swing of 0 to 3.3 V
(3.3 V TTL), the DIO lines cannot drive 5 V CMOS logic levels. To
interface to 5 V CMOS devices, you must provide an external pull-up
resistor to 5 V. This resistor pulls up the 3.3 V digital output from the
NI 781xR to 5 V CMOS logic levels. Refer to Appendix A,
Specifications ,
for detailed DIO specifications.