Serial Interfaces
for RS-485 and RS-232
RS-485 and RS-232 Interfaces
PCI, PXI/CompactPCI, PCMCIA, and ISA Interfaces
Compatible with standard PC serial port
Full Windows 2000/9x Plug and Play
compatibility for switchless
configuration
2, 4, 8, and 16 ports
Handle RTS/CTS hardware
handshake lines
460 kb/s maximum transfer rate
Transmit and receive FIFOs up to
64 bytes
Interrupt-sharing between ports
2000 V isolation
PCI-232, PXI-8420, PXI-8422,
PCMCIA-232, AT-232
RS-232 interfaces
Cable lengths to 15.6 m (50 ft)
Note: Features vary depending
on board model. See detailed
specifications.
Driver Software
NI-Serial for
Windows 2000/NT/Me/9x
PCI-485, PXI-8421, PXI-8423,
PCMCIA-485, AT-485
RS-485 or RS-422 interfaces
Communicates with up to 31 devices
Automatic transceiver-control mode
for 2-wire RS-485 devices
Cable lengths to 1.2 km (4000 ft)
Application Software
LabVIEW
Measurement Studio
Lookout
C/C++
Visual Basic
Any package written to the Microsoft
serial driver interface
Overview
The National Instruments serial interface boards for PCI,
PXI/CompactPCI, PCMCIA, and ISA are asynchronous serial interfaces
for communicating with serial devices. Depending on the platform,
interfaces are available with up to 16 ports and full Windows 2000/9x
Plug and Play compatibility, which gives you the benefit of automatic
configuration for easier installation and maintenance. You can install
and use these boards as standard serial ports from your existing
applications. Development environments such as Visual Basic, Visual
C++, and Excel, as well as our LabVIEW, Measurement Studio, and
Lookout application software products, can access the add-in serial
ports using standard serial I/O functions. All interface devices include
an enhanced serial driver for improved performance, reliable interrupt
sharing between ports, and access to the advanced transceiver
control mode of the RS-485 interface devices.
Cabling
Our 2 and 4-port serial devices are not
shipped with serial interface cables. Two-
port versions use DB-9 male connectors
with standard pin assignments for RS-485
and RS-232 connectors (see Figure 1).
Four-port devices use 10-position modular
phone jacks, so all four connectors can
EXPRESS
CODES
For information or to
buy products online,
visit ni.com/catalog
and enter:
Serial Interfaces
Pin 5
Pin 1
Pin 9
Pin 6
pxi8420
at232
at485
pci232
pci485
pcmcia232
pcmcia485
Figure 1. DB-9 Connector Pin Locations
exist on a single back panel (see Figure 2). When purchasing a 4-port
serial device, you must order cables that convert the phone jacks to
either DB-9 or DB-25 male connectors with standard pin assignments.
In general, you should order four converter cables per 4-port serial
device. Note that a converter cable is not designed to go the full
distance from a 4-port serial interface directly to your instruments. Our
most popular converter cables convert the 10-pin phone jack on a
Pin 1
Pin 10
Isolation
A common problem in many industrial applications is ground loops –
current flowing through the ground line when ground voltage levels
differ between connected devices. On RS-485, this problem results in
a common-mode voltage produced by the difference in ground levels
or by noise induced on both lines. Isolation of serial ports eliminates
this problem and protects the computer system in harsh industrial
environments. The National Instruments PCI, PXI/CompactPCI,
PCMCIA , and AT serial devices are available with optical isolation up
to 2000 V for such applications.
Figure 2. 10-Position Modular Jack Pin Locations
National Instruments
Tel: (512) 794-0100 • Fax: (512) 683-9300 • info@ni.com • ni.com
821
NI [ NATIONAL INSTRUMENTS CORPORATION ]
