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Chapter 2
Hardware Overview
2-2
ni.com
NI-IMAQ I/O devices such as the the NI 8255R have 29 digital I/O lines
with built-in functionality for communicating with external devices, such
as reading quadrature encoder inputs, generating strobe pulses, and writing
to or reading from digital lines.
NI-IMAQ I/O devices have 15 digital input lines—13 optically isolated
lines and two dedicated TTL lines. There are 14 digital output lines—four
optically isolated lines and 10 dedicated TTL lines. Using these signals,
you can dynamically control your lighting or cameras, synchronize with a
conveyor belt, or communicate with relays that control solenoids and other
actuators.
For more information about using the LabVIEW FPGA Module to
implement custom FPGA logic, refer to the examples at
<LabVIEW>\
examples\IMAQ\IMAQ IO FPGA.llb
.
TTL Inputs and Outputs
TTL is a fast-switching 5 V digital signaling standard commonly used for
applications that require high precision, such as camera triggering. TTL
inputs and outputs do not require a separate power supply.
Caution
Do
not
connect voltage or current sources to TTL outputs. Doing so could
damage the NI 8255R.