Chapter1 Introduction
©NationalInstruments Corporation 1-5 SerialHardware and Software for Windows
The isolated PXI boards are designed for applications in harsh
environments.Isolated ports provide reliable communication in situations
involvingground loops from different ground levels or high common mode
voltageinduced on the lines in noisy environments. Non-isolated ports may
not provider eliable communication in those situations. The isolation
between each communicationport and the host PC ensures the safe
operation of the PC and the devicesconnected to other ports on the s ame
board,i n caseof accidental high voltages on communication lines.
The RS-485 boards (PXI-8421 and PXI-8423) support four hardware
transceivercontrol modes for reliable communication with two-and
four-wiredevices. For more information about transceiver control modes,
referto Chap ter 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.
Table1-1 lists the PXI serial board numbers and corresponding board
descriptions.
Table1-1. PXI Board Names and Descriptions
PXI Board Name Description
PXI-8420 RS-232 two port
RS-232 four port
RS-232 eight port
RS-232 16 port
PXI-8421 RS-485 two port
RS-485 four port
RS-485 eight port
PXI-8422 RS-232 two port isolated
RS-232 four port isolated
PXI-8423 RS-485 two port isolated
RS-485 four port isolated