©
National Instruments Corp.
9
FP-CTR-500 and cFP-CTR-500
starts counting again, and the channel status changes to
Overflow
since last read
.
Count Source
Select one of the following count sources from the Value menu:
External Count Input
,
Previous Channel
,
1 kHz Reference
,
or
32 kHz Reference
. Select
External Count Input
,
1 kHz
Reference
, or
32 kHz Reference
to configure the channel so that
it counts low-to-high (off-to-on or rising-edge) transitions of the
count source.
Select
Previous Channel
if you want the channel to count the
number of times that the previous count-input channel reaches
its terminal value and resets to 0. You can configure multiple
counters to operate as one large counter. You can slave Channel 1
to Channel 0, Channel 0 to Channel 7, Channel 7 to Channel 6, and
so on. If you select this option for all of the channels, no counting
occurs.
Gate Source
Select
Gate Input 0–3
from the Value menu to associate a
gate-input channel with a count-input channel. If the count-input
channel uses one of the external gate inputs, counting is enabled
when the gate-input signal is high and is disabled when the signal
is low, as shown in Figure 6. The external device determines the
high and low intervals of the gate-input signal. If you do not
associate a gate-input channel with the count-input channel, select
Always Disabled
or
Always Enabled
. Select
Always Enabled
if
you want the count-input channel to count at all times, even if there
is nothing wired to the gate input. Always Enabled is the default
value.
Figure 6.
Gate Source Set to an External Gate Input
0
0
1
2
3
3
3
3
4
5
6
6
Gate
Input
Count
Input