Introduction
Wiring
The is an active device that interfaces between RS-232 and RS485 serial data networks. Unlike RS-232, the RS-485 uses one cable
pair for each signal path. This balanced system has the advantage of
being much less affected by electrical noise. RS-232 uses one wire per
signal with a common ground return and is specified to around 15
meters. RS-485 is specified for cable lengths of 1200m at 9600 baud.
Using slower datarates, greater distancesmay be achieved.
The can be used in single or multi-drop networks in 2-wire or 4wire mode. It is advisable to use quality twisted pair shielded cable with
the shield connected to the DB-9 shellat both ends.
0080
0080
The device is designed to plug directly into a DB-9 serialport on the back
of a PC or Rinstrum indicator. If the PC has a DB-25 connector, a DB-9
male to DB-25 adaptor cable will need to be made. Alternatively use a
commonly available DB-25 to DB-9 serial port adaptor. The Pin Outs
table on page 2 shows the DB-25 pin numbers to connect to make an
adaptor cable.
Pin 1 on the RS-232 port can also be used to supply power. This power
in is optional and is not needed if the 12VDC adaptor is used. Some
Rinstrum indicators supply power on this pin (eg. the 2100), in which
case the adaptor is not required. Rinstrum can supply a suitable
adaptor if necessary.
0080
RS-232 to RS-485
Converter
User Manual
0080
RS-232 to RS-485
Converter
2-Wire Mode
The can also be used in 2-wire mode. In this case both the
transmitter and receiver share one cable pair. The transmitting RS-232
unit has to signal the to turn on its transmitter. This is done by the
software of the RS-232 device driving the RTS line active when it is
transmitting. Not all Rinstrum indicators will support 2-wire half duplex
modes. If the application only requires one-way communications, (eg.
from an indicator to a remote display), use the bypass RTS pin to turn
the RS-485 transmitter on permanently. The use of 4-wire mode is
recommended for two-way communication to avoid possible data
collisions.
0080
0080
Cabling Example 1
Cabling Example 2
Pair 1
DB-9 Female (from back)
0080 End
1
9
0080 to Remote Device in 2-Wire Half Duplex Mode
(requires RS-232 to use RTS signaling)
To 2-Wire device
B
A
To 2-Wire device
B
A
DB-9 Female (from back)
Pair 1
0080 End
1
4
5
9
0080 to Remote Device in 2-Wire Transmit Only Mode
0080-600-300Page 1Page 4
4-Wire Mode
The can be connected in either 4-wire or 2-wire modes. In 4-wire
mode a separate cable pair is used for both receive and transmit. In this
case the transmitter and receiver are separated and it is not necessary
for the RS-232 device to toggle the RTS (request to send) line when it
transmits. The will however still expect the RTS line from the
transmitting device to be active. RS-232 active is 12V on pin 7. If the
device being transmitted from, does not support this, the “Bypass RTS”
pin should be bridged (eg. connect pin 4 of the RS-485 port to pin 5
GND). This effectively turnsthe RS-485 transmitter on permanently.
The figure below shows the connections when connecting in 4-wire
mode to any Rinstrum indicator.
0080
0080
Pair 1
Pair 2
DB-9 Female (from back) DB-9 Female (from back)
0080 End Remote Device End
11
4
5
99
0080 to Rinstrum Indicator in 4-Wire Mode
RS-485 (male DB-9)
connector
Power Adapter
(9-12V DC 100mA)
Power in connector
(6.1mm centre +)
RS-232 (female DB-9)
connector
Pin Outs
0080 Ports
Page 3Page 2
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