Chapter1 Introduction
SerialHardware and Software for Windows 1-4 ni.com
Theisolated PCI-232 and PCI-485 boards are designed for applications in
harshenvironments. Isolated ports provide reliable communication in
situations involvingground loops from different ground levels or high
common modevoltage induced on the lines in noisy environments.
Non-isolated ports may notprovide reliable communication in those
situations.The isolation between each communication port and the host PC
ensuresth esafe operati on oft he PC and the devicesconnected to ot her
ports on the same board, in case of accidental highvoltages on
communication lines.
The PCI-485 boards support four hardware transceivercontrol modes
for reliable communication with two- and four-wire devices.For more
information about transceivercontrol modes, refer to Chapter 6, Using
Your Serial Hardware.
Alls erial hardwareuses standard 16550-compatible UARTs (Universal
Asynchronous Receiver/Transmitters)for complete compatibility
with standard PC COM ports. The serial hardware contains FIFOs
(First-In-First-Out) buffersto reduce su sceptibility to interrupt latency
for fastertran smission rates. Full Plug and Play compatibility allows
switchless configurationand in stallation. Form ore information about
the serial hardwarespecifications and operating conditions, refer to
Appendix E, Specifications.
PXI Kits
The serialhardware gives you a variety of solutions for serial
communication. The RS-232 boards (PXI-8420 and PXI-8422) work with
theRS-232 protocols. The RS-485 boards (PXI-84 21a nd PXI-8423) work
withthe RS-422 and RS-485 protocols. You can use the RS-232 boards for
serialcommunication up to distances of 50 ft. You can connect the RS-485
boardstoupto31devicesusingserialcablelengthsupto4,000ft.
Additionally,the PXI serial boards are available in a two-port version, a
four-portversion, an eight-port version (PXI-8420 and PXI-8421 only),
and a 16-port version(PXI-8420 only). The two-port versions use DB-9
connectors. The four-port versionsuse 10-posit ion modular jacks to
provideall four con nections on a single front panel. Optional cable
accessoriesconvert the 10-position modular jacks to either DB-9 or DB-25
connectorswith standard pinouts. The eight-port versions use two different
adapter cables to convertthe 68-pin connector on the board to eight DB-9
connectors.The 16-port version uses a breakout box to convert the 100-pin
connector on the board to sixteen DB-9 connectors. Throughout this
manual, PXI serial boards refers to all versions of the PXI serial boards.