4WSD9R1203-1/4
© 2003 by B&B Electronics. All rights reserved.
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PRODUCT INFORMATIONPRODUCT INFORMATIONPRODUCT INFORMATIONPRODUCT INFORMATION
Table 1:
RS-232 Pinout
Pin #
Signal
1
DCD
2
RD
3
TD
4
DTR
5
GND
6
DSR
7
RTS
8
CTS
Table 2:
RS-422/485 Pinout
Pin #
Signal
2
RD(A)-
3
TD(B)+
4
GND
6
GND
7
RD(B)+
8
TD(A)-
Model 4WSD9R
Universal Converter
Covers All the Bases-
RS-232 to 4-wire RS-422,
2-wire or 4-wire RS-485
The 4WSD9R Universal Converter is a port-powered or externally powered two-channel RS-232 to RS-422/RS-485
converter. It converts TD and RD RS-232 lines to balanced RS-422 or RS-485 signals. RS-485 is an enhanced version
of the RS-422 standard, allowing multiple drivers and receivers on a two-wire system. The unit is powered from the RS-
232 data and handshake lines whether the lines are high or low. Or, if there is not enough power on the port, it can be
powered by an ex12VDC 100mA supply. The 4WSD9R has DB-9 female connectors on both the RS-232 side
and the RS-485 side. The RS-232 connector is configured as DCE (like a modem).
RS-232 Side:
Connector:
DB-9 female (DCE)
Signals:
Passes through pins 3 (TD) and 2 (RD)
Pins 7 (RTS) and 8 (CTS) are tied together
Pins 4 (DTR), 6 (DSR), and 1 (CD) are tied together
RS-422/RS-485 Side:
Connector:
DB-9 female
Signals:
RS-485 2-wire half-duplex, or RS-485 4-wire full-duplex,
or RS-422 4-wire full-duplex depending on switch configurations
Automatic control circuit enables driver only when transmitting
Receiver can be disabled when transmitting to prevent echo back to RS-232 device when in 2-wire mode
Data Rates:
Up to 115.2 kbps
Distance:
Externally powered transmits up to 4000 ft (1200 m) at 115.2 kbps (may be less with port powering)
Dimensions:
3.0 x 1.6 x 0.8 in (7.8 x 4.3 x 2.0 cm)
Power
No external power is required if two RS-232 output handshake lines are available and the cable
run is short. If the handshake lines are raised and no termination is used, the power efficiency is
greatly increased. Less than 3mA is required to operate the 4WSD9R plus the load current. For
applications that do not have handshake lines or require a large load current, power may be
externally supplied with a +12VDC power supply with a 2.5mm plug (tip positive).
RS-232 Operations
The RS-232 port has a female DB9 connector with pins 2 (RD), 3 (TD), and 5 (Signal Ground)
supported. Pins 7 (RTS) and 8 (CTS) are tied together, and pins 6 (DSR), 1 (DCD), and 4
(DTR) are also tied together. Any incoming data lines in either the high or low state are used to
port power the 4WSD9R. The more handshake lines available, the more likely the unit can be
port powered. Table 1 shows the RS-232 pinout.
RS-422/485 Operations
Although the 4WSD9R can use handshake lines to power the converter, no handshaking is
required to control the RS-422/RS-485 driver. With switch 1 set to RS-422, the driver is
always enabled. When switch 1 is in the RS-485 position, the RS-485 driver is automatically
enabled during each spacing state on the RS-232 side. During the marking or idle state, the
RS-485 driver is disabled and the data lines are held in the marking state by the 4.7K Ohm pull-
up and pull-down resistors. The value of these resistors may need to be changed to a different
value when termination is used in order to maintain the proper DC bias during the idle state.
See B&B Electronics’ free RS-422/RS-485 Application Note for more information on termination
and DC biasing of an RS-485 network.
