© National Instruments
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RS-485/422 Serial Port
The cDAQ chassis has an RS-485/422 serial port, COM 2, accessible through a 10-position
RJ-50 modular jack. The shield of the RJ-50 connector is isolated from the chassis, enabling you
to use shielded cables while maintaining isolation. The RS-485/422 serial port is shown in
Figure 1-1. Refer to Figure 1-20 for pin locations and signal descriptions.
Figure 1-20.
RS-485/422 Serial Port Pin Locations
COM 2 is designed to operate in four-wire (RS-422) or two-wire mode.
NI offers a DIN rail-mountable screw terminal adapter (NI part number 778674-01) that you can
use to connect termination resistors to COM 2.
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.
Go to
ni.com/info
and enter Info Code
exswh5
for up-to-date information about supported
NI devices for the NI cDAQ-9138/9139 chassis.
MXI-Express Port
You can use the cDAQ chassis MXI-Express port, shown in Figure 1-1, to connect to a
MXI-Express chassis. The NI cDAQ-9138/9139 for Windows chassis support all
NI MXI-Express chassis. Currently, the NI cDAQ-9138/9139 for LabVIEW Real-Time chassis
support the RIO expansion chassis. Go to
ni.com/info
and enter Info Code
exswh5
for
up-to-date information about supported NI devices for the NI cDAQ-9138/9139 chassis.
Complete the following steps to connect one or more cDAQ chassis to a MXI-Express device.
1.
Make sure the MXI-Express device is configured and powered off.
2.
Make sure the cDAQ chassis is powered off.
3.
Connect the cDAQ chassis to the MXI-Express device using a x1 cable. Refer to Table 1-9
for MXI-Express cable lengths and part numbers.
1 No Connect
2 TXD–
3
TXD+
4 No Connect
5 No Connect
6 RXD–
7 RXD+
8
No Connect
9 No Connect
10 I
s
ol
a
ted GND