Chapter 7
Counters
7-18
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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.
Single Two-Signal Edge-Separation Measurement
With single two-signal edge-separation measurement, the counter counts
the number of rising (or falling) edges on the Source input occurring
between an active edge of the Gate signal and an active edge of the Aux
signal. The counter then stores the count in a hardware save register and
ignores other edges on its inputs. Software then reads the stored count.
Figure 7-20 shows an example of a single two-signal edge-separation
measurement.
Figure 7-20.
Single Two-Signal Edge-Separation Measurement
Buffered Two-Signal Edge-Separation Measurement
Buffered and single two-signal edge-separation measurements are similar,
but buffered measurement measures multiple intervals.
The counter counts the number of rising (or falling) edges on the Source
input occurring between an active edge of the Gate signal and an active
edge of the Aux signal. The counter then stores the count in a hardware save
register. On the next active edge of the Gate signal, the counter begins
another measurement. A DMA controller transfers the stored values to host
memory.
AUX
Co
u
nter
Armed
8
0 0 0 0 1 2
3
4 5 6 7 8 8 8
Me
asu
red Interv
a
l
GATE
S
OURCE
Co
u
nter V
a
l
u
e
HW
Sa
ve Regi
s
ter
