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QUICK START
GUIDE
Document Number: 710-11187- 00_422CEC_ 2217qsg
Before you begin, be
sure you have the following:
Model 422CEC
8-Channel RS-232 to RS-422 Converter
+ 422CEC Serial Converter
+ 12 VDC Power Supply (sold separately)
Recommended Accessories
422CEC Schematic Diagram
6
12 VDC Power Supply, 6 W,
Int’l AC Input, 2.5mm Plug
# SMI6-12-V-P230-C1
Serial Adapter Cable,
DB9F to DB25M, 6 ft (1.8m)
# 232CAM
RS-232 DB25
Female Port (DCE)
Getting Started
1
Model 422CEC, RS-232 to RS-422 converter converts
unbalanced RS-232 signals to balanced RS- 422 signals.
Ten RS-422 receivers can be connected in parallel to any
one RS-422 driver for use in multidrop systems.
The RS-422 Standard uses a balanced voltage digital
interface to allow communications of 90K bits per second
on cable lengths of 4000 feet (1219 meters). If this baud
rate is exceeded the line length will decrease accordingly.
Product Overview
Polarity
2
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” terminal should be negative with respect to
the “B” terminal.
422CEC SPECIFICATIONS
Data Rate Up to 115.2K baud
Signals
Converts eight RS-232 c hannels
to RS- 422
Signals
Supported
TD, RD, RTS, CTS, DTR, DS R, DCD,
spare
Power
10-30 VDC, 110 mA (unloaded)
Additional current for external loading.
RS-232 DB25 Male Por t
(EIA-530 pinouts)
Extend RS-232
lines up to
4000 ft (1219 m)
Termination Resistor
3
The wire recommended in the RS- 422 Standard is number
24 AWG copper conductor, twisted-pair telephone cable with
a shunt capacitance of 16pF per foot.
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
necessar y to use a termination resistor that is larger than
100 O hms.
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
resistors, line lengths, grounding, etc.
Protective Ground
4
Figure 1. Interconnection of Two 422CEC Converters
Figure 1 below shows the interconnection of two (2)
422CEC converters. This allows you to extend your
RS-232 line up to 4000 feet. If you do not require all the
handshake lines, you may leave these disconnected.
RS-232 Signal Distance
5
The RS- 422 Standard recommends that Protective
Ground (pin 1) be connected to a good “green wire”
ground. This may be already connected in your RS-232
equipment.
Protective Ground and Signal Ground should be
connected through to each end of the system and be
connected to each other using a 100 Ohm 1/2 Watt
resistor at one end only. If a shielded twisted pair is used
the shield should be connected to Protective Ground.
Power Jack
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