Document No. 422LP25N4300 - pg. 1/2
1993 B&B Electronics -- Revised November 2000
This product designed and manufactured in USA of domestic and imported parts by
Port-Powered RS-232 to RS-422 Converter
CE
CE
CE
CE
With DB-25 Connectors
Model 422LP25N
This RS-232 to RS-422 converter converts unbalanced RS-232 signals to balanced RS-422 signals. The power used for this
converter is derived from the transmit data line (pin 2) and the handshake control lines (pins 4, 5, 6, 8, and 20). The converter can
derive power from these lines when they are in the positive or negative voltage state. This permits the converter to be used in
applications without any regard to software control of the handshake lines. If no handshake lines are available and all power must be
derived from the transmit data line, the converter can drive limited cable lengths. A guide for this condition would be to drive only
several hundred feet of transmission line and not to terminate the transmission line with a resistor of less than 1000 ohms. When
more handshake lines are available longer lengths of cable can be driven. This converter has been tested at 115.2k baud with 4000
feet of cable. For applications where handshake lines are not available and long cable runs are involved, an external power supply
can be connected to the female connector on the RS-422 side of the converter on pins 12 (Gnd) and 25 (+12).
NOTE: When using an external supply, the supply should be connected only to specifically labeled power inputs (power jack,
terminal block, etc.). Connecting an external power supply to the handshake lines may damage the unit. Contact technical
support for more information on connecting an external power supply to the handshake lines.
The RS-232 port uses a male DB-25 type of connector with pins 2 (TD input) and 3 (RD output) supported. Signal Ground is
pin 7 on both the RS-232 and RS-422 sides.
Interconnection of the converter with another RS-422 device:
1.
The polarity of the two RS-422 lines must be correct. With no data being sent, the RS-232 line should be negative and the
RS-422 "A" pin 2 should be negative with respect to the "B" pin 14.
2.
The wire recommended in the RS-422 Standard is number 24 AWG copper conductor, twisted-pair telephone cable with a
shunt capacitance of 16 pF per foot.
3.
For long runs and/or high data rates it is recommended that the wires be terminated with a resistor at the receive end. The
twisted pair usually used has an impedance of about 100 ohms, therefore a 100 ohm resistor is normally used for the
termination. The RS-422 side of the converter requires more power as the transmission line is increased and as the
termination resistor value is reduced, therefore it may be necessary to use a termination resistor that is larger than 100 ohms.
4. The RS-422 driver has the ability to drive 10 RS-422 receivers connected in parallel. A system of multiple receivers may require
some experimentation with location and size of termination resistors, line lengths, grounding, etc.
DECLARATION OF CONFORMITY
Manufacturer's Name:
B&B Electronics Manufacturing Company
Manufacturer's Address:
P.O. Box 1040
707 Dayton Road
Ottawa, IL 61350 USA
Model Numbers:
422LP25N
Description:
Port-powered RS-422 Converter
Type:
Light industrial ITE equipment
Application of Council Directive: 89/336/EEC
Standards:
EN 50082-1 (IEC 801-2, IEC 801-3, IEC 801-4)
EN 50081-1 (EN 55022, IEC 1000-4-2)
EN 61000 (-4-2, -4-3, -4-4, -4-5, -4-6, -4-8, -4-11)
ENV 50204
EN 55024
Michael J. Fahrion, Director of Engineering
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