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SCXI Chassis and Module with
RS-232/RS-485 Interface
SCXI-2000, SCXI-2400
NI-DAQ Software
Windows NT
Window 95
Windows 3.1
Remote signal conditioning and
data acquisition
RS-232 and RS-485 serial interfaces
Range up to 1.2 km (4,000 ft) (RS-485)
Networks up to 31 SCXI chassis
(RS-485)
Controlled by NI-DAQ software
Same API as local SCXI
Transparent serial communication
Application Software
LabVIEW
BridgeVIEW
LabWindows/CVI
ComponentWorks
Measure
VirtualBench
Lookout
SCXI-2000 Chassis
4-slot chassis
RS-232/RS-485 interface
Low-noise environment
Fully shielded enclosure
Low-noise power system
Integrated SCXIbus system
Accepts any SCXI modules
SCXI-2400 Module
RS-232/RS-485 adapter
Operates in any SCXI-100X chassis
Overview
The SCXI-2000 and SCXI-2400 provide SCXI systems with an
RS-232/RS-485 serial interface that is useful for implementing
remote or distributed data acquisition (DAQ) systems. The
optically isolated RS-485 interface provides a reliable, long-
distance connection (1,200 m or 4,000 ft) of multiple SCXI chassis
to PCs. Alternatively, you can use the RS-232 interface for a very
convenient direct connection to the standard serial port on the
PC. The SCXI-2000 is a chassis with a built-in RS-232 and RS-485
interface. Similar to the standard SCXI-1000 chassis, the SCXI-
2000 can house up to four SCXI signal conditioning and data
acquisition modules. The SCXI-2400 module adds an RS-232 and
RS-485 interface to any standard SCXI chassis, including the
12-slot SCXI-1001 chassis and SCXI-1000DC DC-powered chassis.
The SCXI-2000 and SCXI-2400 include NI-DAQ for Windows
driver software, a dynamic driver library (DLL) that provides high-
level, easy-to-use functions that you can call from LabVIEW,
LabWindows/CVI, ComponentWorks, or any Windows
programming environment. NI-DAQ handles all the details of
programming the SCXI system, as well as the serial
communications between the host computer and SCXI chassis.
In fact, the programming interface for using an SCXI system with
an RS-232 or RS-485 interface is the same as for an SCXI system
using a plug-in DAQ board or direct parallel port interface.
communications processor within the SCXI-2000 and SCXI-2400
handles all serial communications with the PC, transferring data
and commands to modules via the SCXIbus in the backplane of
the chassis.
The SCXI-2000 and SCXI-2400 have two serial ports – RS-232
and RS-485. You can use the RS-232 port to connect the SCXI
system directly to the standard serial port of a PC (Figure 1). If your
system requires more chassis and/or longer distance communica-
tions, you can use RS-485. The RS-485 port supports multidrop
configurations, so you can connect up to 31 SCXI chassis,
including up to 16 chassis with analog inputs, on a single RS-485
network. Figure 2 illustrates a sample RS-485 system using both
SCXI-2000 chassis and SCXI-2400 modules.
If any analog inputs are needed, an SCXI-1200 DAQ module
installed in the chassis performs the analog-to-digital conversion
of conditioned output signals from other SCXI signal conditioning
modules. The digitized data is transferred via a high-speed
parallel connection to the SCXI-2000 chassis or SCXI-2400
module, which handles the communications via the serial port to
the PC. The cable for this parallel connection is included with the
SCXI-2000 and SCXI-2400. If the chassis includes only analog
output, digital I/O, or relay modules (no analog input modules)
then you do not need to install an SCXI-1200 DAQ module into
the chassis; the SCXI-2000 or SCXI-2400 can communicate
directly with these modules.
Description
System Configurations
You can use any combination of SCXI signal conditioning and
data acquisition modules with the SCXI-2000 or SCXI-2400. The
Backplane Operation
The SCXI-2000 chassis, like the SCXI-100X chassis, integrates the
operation of multiple SCXI modules. The SCXIbus in the
National Instruments
Phone: (512) 794-0100 • Fax: (512) 794-8411• info@natinst.com • www.natinst.com
391
SCXI Chassis and Module with
RS-232/RS-485 Interface
Host PC
Host PC
RS-232
RS-232
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SCXI-100X
Chassis with
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SCXI-2000
Chassis
Figure 1. You can cable an SCXI-2000 or an SCXI-100X chassis with the SCXI-2400 module directly to the RS-232 port of a PC.
Host PC
AT-485 Plug-In
RS-485 Interface
RS-485
RS-485
To Addiitonal
SCXI Chassis
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Chassis with
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SCXI-2000
Chassis
Figure 2. You can connect multiple remote SCXI chassis (SCXI-2000 chassis or SCXI-100X chassis with SCXI-2400
module) on a single RS-485 network for remote or distributed DAQ applications.
backplane of the SCXI-2000 chassis includes guarded analog
buses for signal routing and digital buses for transferring data
and timing signals among modules. For example, you can use
an SCXI-1200 module to acquire signals from multiple SCXI
signal conditioning modules. In this mode, the SCXI-2000
chassis uses the backplane SCXIbus to synchronize the
multiplexing of the conditioned analog signals from other
modules in the chassis. The SCXI-2000 and the SCXI-2400 also
use the backplane SCXIbus to communicate digital data and
commands to SCXI modules in the chassis.
Functionally, the SCXI-2000 chassis is a superset of the
SCXI-1000 chassis. Therefore, you can use the SCXI-2000 chassis
in SCXI-1000 mode and connect the SCXI system directly to the
PC parallel port (with the SCXI-1200) or to a plug-in DAQ board.
used in RS-485 mode, switches on the chassis set the network
address of the chassis. The SCXI-2000 and SCXI-2400 kits include
termination resistors for the RS-485 network. The RS-485 port is
optically isolated to ensure reliable performance even in noisy
environments. Network connections are made with four screw
terminals provided on a removable plug.
Figures 3 and 4 show the connectors and switches on the
front of the SCXI-2000 chassis. Connectors and switches on the
SCXI-2400 module are similarly located. For communications
over the serial network to the host PC, the SCXI-2000 and SCXI-
2400 use an efficient binary protocol to optimize data
throughput. The protocol incorporates High-Level Data Link
Control (HDLC) protocol for reliable data transfer with CRC
routines and retransmittal of lost or corrupted data. In addition,
memory onboard the SCXI-2000 and SCXI-2400 is used to buffer
data collected from SCXI modules before transmittal across the
serial link to the host PC.
Communications
The SCXI-2000 and SCXI-2400 include an RS-232 and RS-485
port for communications to the host computer at baud rates up
to 57.6 kbaud/s (switch-selectable). The RS-232 port includes a
9-pin male D-sub connector for easy connection directly to the
serial port of the PC with a null modem cable.
If you need remote or distributed data acquisition capabilities,
you can use the RS-485 port for multidrop, long-distance
configurations up to 1,200 m (4,000 ft). The RS-485 interface is
a full-duplex, four-wire implementation. You can connect up to
31 SCXI chassis to an RS-485 port on the PC provided by an
interface such as a National Instruments AT-485 board. However,
of these 31 chassis only 16 SCXI chassis per PC can include
analog input channels and the SCXI-1200 DAQ module. When
Software
The SCXI-2000 and SCXI-2400 are shipped with NI-DAQ driver
software for Windows. NI-DAQ is a complete, full-function DAQ
driver for use with National Instruments PC-based DAQ
hardware. NI-DAQ also includes a configuration utility for
configuring the serial network and verifying proper operation of
the SCXI system. NI-DAQ hides the low-level programming
details and transparently handles implementation of the
communications protocol. In fact, the programming interface
for an SCXI system with an RS-232 or RS-485 interface is the same
as for an SCXI system used with a plug-in DAQ board or direct
392
National Instruments
Phone: (512) 794-0100 • Fax: (512) 794-8411• info@natinst.com • www.natinst.com
SCXI Chassis and Module with
RS-232/RS-485 Interface
Status LEDs
RS-485 connector
RS-232 connector
Parallel connector
(to SCXI-1200)
Baud rate and
address selection
Figure 3. Front Panel of SCXI-2000 Chassis
Figure 4. Back Panel of SCXI-2000 Chassis
parallel port interface. Therefore, you can reuse code across
many types of SCXI systems, whether configured for remote,
portable, or benchtop data acquisition and control. You can also
use the SCXI-2000 and SCXI-2400 products with National
Instruments application software packages, which use NI-DAQ
driver software.
Part Numbers
SCXI-2000 chassis with NI-DAQ software*
U.S. 120 VAC .............................................777140-01
Swiss 220 VAC ...........................................777140-02
Australian 240 VAC ....................................777140-03
Universal Euro 240 VAC.............................777140-04
No. American 240 VAC .............................777140-05
United Kingdom 240 VAC .........................777140-06
Japan 100 VAC ..........................................777140-07
SCXI-2400 Module
with NI-DAQ software*..............................777284-01
Accessories
The SCXI-2000 and SCXI-2400 are shipped with a 2 m RS-232
null modem cable with 9-pin, D-Sub connectors. Both products
also include a parallel jumper cable to connect the parallel port
of the SCXI-1200 to the parallel port of the SCXI-2000 chassis or
SCXI-2400 module. Both products also include a removable
protective cover for the baud rate and address switches on the
front panel.
In addition, the rack-mounting, panel mounting and filler
panel accessories are available for the SCXI-2000 chassis. See
SCXI Accessories later in this section for more information.
Optional Accessories
RS-232 null modem cable (9-pin D-Sub)
1 m ............................................................182238-01
2 m ............................................................182238-02
4 m ............................................................182238-04
SCXI-1360 front filler panel................................776576-60
SCXI-1361 rear filler panel .................................776576-61
SCXI-1371 rack-mount kit for
SCXI-2000...................................................776577-71
SCXI-1372 dual rack-mount kit for
SCXI-2000...................................................776577-72
SCXI-1373 panel-mount kit ...............................776577-73
* Includes 2 m RS-232 null modem cable (182238-02), 6 in. parallel port cable
(for SCXI-1200) and NI-DAQ software for Windows NT/95/3.1/3.1J on CD-ROM.
National Instruments
Phone: (512) 794-0100 • Fax: (512) 794-8411• info@natinst.com • www.natinst.com
393
SCXI Chassis and Module with
RS-232/RS-485 Interface
Specifications
Typical for 25º C unless otherwise noted.
Certifications and Compliances
CE Mark Compliance
This product meets applicable EU directive(s) as follows:
Safety isolation....... .............................. Low voltage directive EN 61010
EMC Directive
Immunity.......................................... EN 50082-1:1994
Emissions.......... ............................... EN 55011:1991 Group I Class A at 10 m
Communications
Interface .............................................. RS-232, or RS-485 (four-wire, full
duplex)
Baud rate............................................. 300, 600, 1200, 2400, 4800 or
9600 b/s; 19.2, 38.4, or 57.6 kb/s
Data Throughput
1
1
Throughput for continuous analog input acquisition with one SCXI
chassis, running on a Pentium or 486 PC with a 16550-compatible UART.
2
NI-DAQ driver software supports the use of up to 16 SCXI-1200 DAQ
modules (required for analog inputs) per PC.
3
Dimensions do not include SCXI terminal block mounted to front of chassis, which
adds 7.5 cm to depth.
Baud Rate
Acquisition Rate
(Analog input)
57.6 kb/s
1,500 S/s
38.4 kb/s
1,000 S/s
19.2 kb/s
500 S/s
9600 kb/s
250 S/s
2400 b/s
60 S/s
1200 b/s
30 S/s
Maximum distance
RS-232 ............................................. 30 m (100 ft)
RS-485 ............................................. 1.2 km (4,000 ft)
Number of chassis per serial port
RS-232 ............................................. 1
RS-485
Chassis with analog inputs............. 16
2
Total chassis .................................. 31
Isolation (RS-485) ................................. 42 V, with 750 V common mode
transient suppression
LEDs .................................................... Transmit, receive, online, program, and
test
I/O Connectors
RS-232 port ...................................... Standard 9-pin male D-Sub
RS-485 port ...................................... Screw terminal plug; four signals
(RX+, RX-, TX+, TX-)
Parallel port ..................................... 36-pin MDR 1284-C female connector
SCXI-2000 Chassis Power Requirements
Input voltage ....................................... 100, 120, 220, or 240 VAC at 50 or
60 Hz
Operating current, maximum .............. 0.6 A at 100 VAC, 0.5 A at 120 VAC,
0.25 A at 220 or 240 VAC
Module power available
+5 VDC............................................ 50 mA per slot
+18.5 to +25.0 VDC ........................ 170 mA per slot
-18.5 to -25.0 VDC........................... 170 mA per slot
Physical
SCXI-2000
Dimensions (including fan)
3
............. 18.0 by 19.5 by 24.8 cm
(7.1 by 7.7 by 9.8 in.)
Weight............................................. 3.9 kg (8 lb 10 oz)
SCXI-2400
Dimensions ...................................... 3.0 by 17.2 by 20.3 cm
(1.2 by 6.8 by 8.0 in.)
Environment
Operating temperature........................ 0º to 50º C
Relative humidity ................................. 5% to 90% noncondensing
394
National Instruments
Phone: (512) 794-0100 • Fax: (512) 794-8411• info@natinst.com • www.natinst.com
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