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7-17
Buffered (Sample Clock) Position Measurement
With buffered position measurement (position measurement using a sample clock), the counter
increments based on the encoding used after the counter is armed. The value of the counter is
sampled on each active edge of a sample clock. A DMA controller transfers the sampled values
to host memory. The count values returned are the cumulative counts since the counter armed
event; that is, the sample clock does not reset the counter. You can route the counter sample
clock to the Gate input of the counter. You can configure the counter to sample on the rising or
falling edge of the sample clock.
Figure 7-19 shows an example of a buffered X1 position measurement.
Figure 7-19.
Buffered Position Measurement
Two-Signal Edge-Separation Measurement
Two-signal edge-separation measurement is similar to pulse-width measurement, except that
there are two measurement signals—Aux and Gate. An active edge on the Aux input starts the
counting and an active edge on the Gate input stops the counting. You must arm a counter to
begin a two edge separation measurement.
After the counter has been armed and an active edge occurs on the Aux input, the counter counts
the number of rising (or falling) edges on the Source. The counter ignores additional edges on
the Aux input.
The counter stops counting upon receiving an active edge on the Gate input. The counter stores
the count in a hardware save register.
You can configure the rising or falling edge of the Aux input to be the active edge. You can
configure the rising or falling edge of the Gate input to be the active edge.
Use this type of measurement to count events or measure the time that occurs between edges on
two signals. This type of measurement is sometimes referred to as start/stop trigger
measurement, second gate measurement, or A-to-B measurement.
1
3
1
Ch A
Ch B
3
1
0
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4
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B
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Sa
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(
Sa
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ing Edge)
Co
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Armed
Summary of Contents for PCI-6281
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