Chapter 3
Feature Descriptions
©
National Instruments Corporation
3-9
cFP-20xx and cFP-BP-x User Manual
Figure 3-4 shows how to wire several FP-1001 banks in an RS-485 network
controlled by the cFP-2020. Only two FP-1001 banks are shown, but the
cFP-2020 can control up to 24 FP-1001 banks. Install 120
Ω
termination
resistors at each end of the network as shown in Figure 3-4.
Figure 3-4.
Wiring for an RS-485 Network Controlled by the cFP-2020
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-2020 Only)
The cFP-2020 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.
RXD– RXD+ TXD–
TXD+ RX–
RX+
TX–
TX+
RX–
RX+
TX–
TX+
cFP-2020 COM 4
FP-1001
FP-1001
120
Ω
120
Ω
120
Ω
120
Ω
