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RS232 SERIAL COMMUNICATION
RS485 SERIAL COMMUNICATION
If the RS485 network exceeds 100 metres in length or baud-rate over 9600 are
used, two terminating resistors are needed at the ends of the network. Two
120 ohm resistors must be connected
between the “+” and “–” terminals of the
line, on the terminal strip of the furthest instruments
.
Should there be different
instruments or converters, refer to the specific manuals to determine whether it is
necessary to connect the above-mentioned resistors.
DIRECT CONNECTION BETWEEN RS485 AND RS232 WITHOUT CONVERTER
Since a two-wire RS485 output may be used directly on the RS-232 input of a PC or remote display,
it is possible to implement instrument connection to an RS-232 port in the following manner:
INSTRUMENT
RS232
RS 485
–
→
RXD
RS 485
+
→
GND
This type of connection allows A SINGLE instrument to be used in a ONE WAY
mode.
DB9-F
5
3
2
INSTRUMENT
RS232 TXD
PC
RS232 RXD
GND
INSTRUMENT
RS485 +
RS485 -
max 500 m
RS485
+
3 2
5
PC RS23
2
RX+
RX-
TX-
TX+
CONVLAU
24 VDC
+
-
0
TX
RX
VIN
RS485 +
RS485 -
RS485 -
RS485
+
RS485 -
RS485
+
RS485 -
GND
GND
GND
INSTRUMENT
INSTRUMENT
