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Chapter 2 Function Reference — GPCTR_Change_Parameter
NI-DAQ FRM for PC Compatibles 2-204
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National Instruments Corporation
Use this function with paramID = ND_GATE_POLARITY to select polarity of the gate signal.
paramID =
ND_GATE_POLARITY
This gate signal controls the operation of the general-purpose counter in some applications.
In those applications, you can use polarity of the gate signals to modify behavior of the
counter. Corresponding legal values for paramValue are as follows:
• ND_POSITIVE
• ND_NEGATIVE
The meaning of the two ND_GATE_POLARITY selections is described in the
GPCTR_Set_Application function.
paramID =
ND_Z_INDEX_PULSE
(6602 and 455X devices only)
This parameter allows automatic reloading of counter when a quadrature Z-Index pulse
occurs on the gate when input conditioning is set to one of the quadrature input mode. The
counter is reloaded with a value from 0 to 2
32
– 1.The Z-Index pulse of a quadrature encoder
can be connected to the gate pin. With this setting, the counter will reload every time it sees
a pulse on the gate pin. The Z-Index pulse will be registered only if encoder channels A and
B are both in the low state.
paramID =
ND_RELOAD_ON_GATE (6602 and 455X devices only)
This parameter allows automatic reloading of the counter when a gate edge occurs. The
counter is reloaded to the value set by the paramID =
ND_INITIAL_COUNT. The legal vales
for this are
ND_YES and ND_NO. This paramID with paramValue = ND_YES can be used for
event counting operations that involve quadrature encoders. The Z-Index pulse of a
quadrature encoder can be connected to the gate pin. With this setting, the counter will reload
every time it sees a pulse on the gate pin.
Table 2-25.
Default Gate Selection
gpctrNum
E Series and
445X Devices
6602 Devices 455X Devices
ND_COUNTER_0 ND_PFI9 ND_PFI_38 ND_PFI_30
ND_COUNTER_1 ND_PFI4 ND_PFI_34 ND_PFI_26
ND_COUNTER_2
N/A
ND_PFI_30
N/A
ND_COUNTER_3
N/A
ND_PFI_26
N/A
ND_COUNTER_4
N/A
ND_PFI_22
N/A
ND_COUNTER_5
N/A
ND_PFI_18
N/A
ND_COUNTER_6
N/A
ND_PFI_14
N/A
ND_COUNTER_7
N/A
ND_PFI_10
N/A