NI myDAQ User Guide | © National Instruments | 15
Digital I/O (DIO) and Counters/Timers
There are eight, software-timed DIO lines on the NI myDAQ that can be individually configured
for input or output. Additionally, lines DIO <0..4> can be configured for counter/timer
functionality. The input—accessed through DIO 0, DIO 1, and DIO 2 signals configured as a
counter—is used for counter, timer, pulse width measuring, and quadrature encoding
applications.
When using the counter/timer, the Source is accessed through DIO 0, the Gate through DIO 1,
the Auxiliary Input through DIO 2, the Output through DIO 3, and the Frequency Output
through DIO 4. When using the counter/timer as a quadrature encoder, A, Z, and B correspond
to DIO 0, DIO 1, and DIO 2, respectively. In some instances, the software may refer to the
output lines as PFI as opposed to DIO. Refer to Table 3 for a list of the corresponding
counter/timer signals assignments through the DIO terminals.
For more information about event timing requirements, refer to the NI myDAQ Specifications
document. For more detailed information on using counter/timers with NI myDAQ, refer to the
KnowledgeBase document How Do I Use the NI myDAQ Counter?. To access this document,
go to
ni.com/info and enter the Info Code mydaqcounter.
Table 3. NI myDAQ Counter/Timer Signal Assignments
NI myDAQ
Signal
Programmable
Function Interface
(PFI)
Counter/Timer
Signal
Quadrature Encoder
Signal
DIO 0 PFI 0 CTR 0 SOURCE A
DIO 1 PFI 1 CTR 0 GATE Z
DIO 2 PFI 2 CTR 0 AUX B
DIO 3
*
PFI 3 CTR 0 OUT —
DIO 4 PFI 4 FREQ OUT —
*
Pulse-width modulation (PWM) pulse train measurements are generated through DIO 3
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