Chapter 7 Counters
© National Instruments 7-45 X Series User Manual
Counter n HW Arm Signal
The Counter n HW Arm signal enables a counter to begin an input or output
function.
To begin any counter input or output function, you must first enable, or arm,
the counter. In some applications, such as a buffered edge count, the
counter begins counting when it is armed. In other applications, such as
single pulse-width measurement, the counter begins 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>
• PFI <0..15>
• AI Reference Trigger (ai/ReferenceTrigger)
• AI Start Trigger (ai/StartTrigger)
•PXI_STAR
• PXIe-DSTAR<A,B>
• Analog Comparison Event
• Change Detection Event
A counter’s Internal Output can be routed to a different counter’s HW Arm.
Some of these options may not be available in some driver software.
Counter n Sample Clock Signal
Use the Counter n Sample Clock (CtrnSampleClock) signal to perform
sample clocked acquisitions and generations.
You can specify an internal or external source for Counter n Sample Clock.
You also can specify whether the measurement sample begins on the rising
edge or falling edge of Counter n Sample Clock.
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