National Instruments NI VISION PCI-8254R 用户手册

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 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.

Do not connect voltage or current sources to TTL outputs. Doing so could 

damage the NI 8254R.