©NationalInstruments Corporation A-1 SerialHardware and Software for Windows
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Connector Descriptions

Connecting Cables

Forthe PCMCIA serial cards and two-port PCI, PXI, and AT serial boards,
you can usethe standard DB-9 connector found on most serial cables.
To uset heD B-9 connector with the four-port serial boards, you need the
10-positionmodular jack to D B-9 cable, whichis availablefrom National
Instruments. You can also use a DB-25 connector with the four-port serial
boardsby ordering the 10-posi tion modular jack to DB-25 converter cable
from National Instruments. The eight-port serial boards include a pig tail
cable adapter, providing eight standard DB-9 connectors. The 16-port
boards include a break out box, providing 16 standard DB-9 connectors.
Note Toachieve the specified isolation voltage for four-port isolated PCI or ATserial
boards,u se only the 10-position modular jack to DB-9 cable included in your four-port
isolated PCI or ATserial board kit.
Formore informat ion about cable connectors, see the connector
descriptions in this appendix.

Connecting Two-Wire Devices

ThePCI-48 5, PCMCIA-485, RS-485 PXI (PXI-8421 and PXI-8423), and
AT-485boards are designed to work with either two- or four-wire devices.
Ify ou 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
communicationin both directions, so you must connect both the transmitter
andthe receiver at each end of the same pair of wires. For example, to
connect anR S-485 data acquisition deviceto a port on your boa rd using
half-duplexcommunication, you need a single twisted pair of wires. At the
board,co nnect 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.Connect the other end of this wire to both the TXD+ and RXD+
signalson the data acquisition device. Use the same method to connect the
TXD–andRXD–signals (pins 9 and 5 on a DB-9 connector, pins 22 and 7
on a DB-25 connector) to the second wire.