Chapter 3
Feature Descriptions
cFP-21xx and cFP-BP-x User Manual
3-10
ni.com
COM 4 is designed to operate in four-wire mode as shown in Figure 3-4.
You can use COM 4 in two-wire mode, but you must design your
application so that it filters out the writes that echo back over the read
channels. NI does not recommend this method.
NI offers a DIN rail–mountable screw terminal adapter that you can use to
connect termination resistors to COM 4. The adapter is part number
778674-01.
Cable adapters for the 10-position modular jacks are available from NI.
Part numbers 182845-01, -02, and -03 are 1, 2, and 3 m cable adapters for
connecting the 10-position modular jack to a 9-position D-Sub plug.
External Switch Inputs and LED Outputs (cFP 2120 Only)
The cFP-2120 has two switch inputs and two LED outputs that you can use
to connect a simple operator interface to the controller. Refer to Figure 1-1
for the location of the input and output terminals. The inputs and outputs
appear in software as Input 1, Input 2, LED A, and LED B. Logic high for
the DIO ports is
+
5 V. Logic low is 0 V. The DIO ports are not isolated and
are not intended for field connections. Use them only for simple VI controls
and indicators.
Outputs 1 and 2 are tied to LEDs A and B, respectively, on the cFP-2120
front panel. When LED A has a value of 1 or 2, Output 1 is ON and sources
+5 V. When LED A has a value of 0, Output 1 is OFF and does not source
voltage. When LED B has a value of 1, Output 2 is ON and s5 V.
When LED B has a value of 0 or 2, Output 2 is OFF and does not source
voltage. You can use the outputs to provide status or alarm indicators to
operators. For example, if the Compact FieldPoint bank is mounted in a
sealed enclosure, you can connect the outputs to external LEDs so that
operators can see status information without opening the enclosure.
You can use the two switch inputs to control the cFP system from
LabVIEW. For example, one switch input could be a START/STOP switch,
and the other could determine which of two VIs should run at startup. NI
recommends connecting a single-pole single-throw (SPST) switch between
the input terminal and one of the C terminals. The switch inputs have a
value of 1 when the switch is closed and 0 when the switch is open.
