Chapter 2
Installation and Verification
PCI Serial for Windows 95
2-10
©
National Instruments Corporation
Figure 2-8 shows how to connect the cables when you install a four-port
version of the PCI serial board.
Figure 2-8. Connecting the Cables to Your Four-Port PCI Serial Board
Connecting Two-Wire Devices
The PCI-485 boards are designed to work with either two- or four-wire
devices. If you are using a two-wire device, refer to the device
documentation for specific wiring instructions.
In general, half-duplex networks use a single twisted pair of wires for
communication in both directions, so you must connect both the transmitter
and the receiver at each end of the same pair of wires. For example, to
connect an RS-485 data acquisition device to a port on your PCI-485 using
half-duplex communication, you need a single twisted pair of wires. At the
PCI-485, you should connect the TXD+ and RXD+ signals (pins 8 and 4
on a DB-9 connector, pins 5 and 20 on a DB-25 connector) together and to
one wire. You should connect the other end of this wire to both the TXD+
and RXD+ signals on the data acquisition device. You use the same method
to connect the TXD- and RXD- signals (pins 9 and 5 on a DB-9 connector,
pins 22 and 7 on a DB-25 connector) to the second wire.
, for information on setting
the transceiver mode for two-wire communication. Refer to Appendix C,
, for more information on duplex architectures.
Serial Board
Additional
Serial Cable
Additional
Serial Cable
10-Position Modular Jack
to DB-9 Cable
10-Position Modular Jack
to DB-25 Cable
485 Terminator
(485 Boards Only)