National Instruments PCI-8430 User Manual

ConnectingTwo-WireDevices
TheNIRS-485hardwareis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
boardusinghalf-duplexcommunication,youneedasingletwistedpairof
wires.Attheboard,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.ConnecttheotherendofthiswiretoboththeTXD+and
RXD+signalsonthedataacquisitiondevice.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aboutsettingthetransceivermodefortwo-wire
communication,refertoRS-485TransceiverControl.Formore
informationaboutduplexarchitectures,refertoSerialPortInformation.

National Instruments PCI-8430 Specifications

General

Operating Temperature	0 °C to 55 °C
Data Bits	5, 6, 7, 8
Stop Bits	1, 1.5, 2
Interface Type	RS-232
Bus Interface	PCI
Data Rate	Up to 1 Mbit/s
Maximum Baud Rate	1 Mbit/s
Baud Rate	50 bps to 1 Mbps
Isolation Voltage	500 V
Parity	None, even, odd, mark, space
FIFO Buffer Size	128 bytes per port
Operating System Compatibility	Windows