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Chapter 7 Counters
NI 6238/6239 User Manual 7-30 ni.com
waiting for the Gate signal when it is armed. Counter output operations can
use the arm signal in addition to a start trigger.
Software can arm a counter or configure counters to be armed on a
hardware signal. Software calls this hardware signal the Arm Start Trigger.
Internally, software routes the Arm Start Trigger to the Counter n HW Arm
input of the counter.
Routing Signals to Counter n HW Arm Input
Any of the following signals can be routed to the Counter n HW Arm input.
•RTSI<0..7>
• Input PFI <0..5>
• ai/ReferenceTrigger
• ai/StartTrigger
•PXI_STAR
Counter 1 Internal Output can be routed to Counter 0 HW Arm. Counter 0
Internal Output can be routed to Counter 1 HW Arm.
Some of these options may not be available in some driver software.
Counter n Internal Output and Counter n TC Signals
Counter n TC is an internal signal that asserts when the counter value is 0.
The Counter n Internal Output signal changes in response to Counter n TC.
The two software-selectable output options are pulse on TC and toggle
output polarity on TC. The output polarity is software-selectable for both
options.
Routing Counter n Internal Output to an Output
Terminal
You can route Counter n Internal Output to any output PFI <6..9> or
RTSI <0..7> terminal. All output PFIs are set to high-impedance at startup.
Frequency Output Signal
The Frequency Output (FREQ OUT) signal is the output of the frequency
output generator.