National Instruments NI VISION PCI-8254R - Manual (Page 13)

Chapter 2 Hardware Overview
NI PCI-8254R User Manual 2-2 ni.com
Using National Instruments RIO hardware and the LabVIEW FPGA
Module, you can define your hardware without in-depth knowledge of
hardware design tools or hardware description languages (HDL). When the
signal requirements change, the LabVIEW code can be modified and
downloaded to the FPGA to change the I/O mix or type. This flexibility
allows you to reuse the same hardware and software at no extra expense.
NI-IMAQ I/O devices such as the such as the NI 8254R, the NI 8255R, and
the NI CVS-1450 Series 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 isolated 24 V lines
and two dedicated TTL lines. There are 14 digital output lines—four
isolated 24 V 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.
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 8254R.