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2.1.2
RS485 Interface (COM1)
The RS485 communication port is located on the rear of the relay and can be connected using a suitable RS485
120 Ohm screened twisted pair cable.
The RS485 electrical connection can be used in a single or multi-drop configuration. The RS485 master must
support and use the Auto Device Enable (ADE) feature. The last device in the connection must be terminated
correctly in accordance with the master device driving the connection. The relays are fitted with an internal
terminating resistor which can be connected between A and B by fitting an external wire loop between terminals
18 and 20 on the power supply module.
The maximum number of relays that can be connected to the bus is 64.
Each relay has an internal terminating resistor – this can be connected in circuit where necessary.
The following settings must be configured when using the RS485 interface.
Setting name
COM1-RS485 Protocol
COM1-RS485 Baud
Rate
COM1-RS485 Parity
COM1-RS485 Mode
Unsolicited Mode
Destination Address
Figure 2-2
©2013 Siemens Protection Devices Limited
Range
OFF, IEC60870-5-103,
MODBUS-RTU, DNP3.0
75 110 150 300 600 1200
2400 4800 9600 19200
38400
NONE, ODD, EVEN
Local, Local or Remote,
Remote
DISABLED ENABLED
0 ... 65520
Communication to Multiple Devices using RS485 (Standard Port)
Chapter 4) 7SR23 DAD Data Communications
Default
Setting
IEC60870-5-
As Required
103
19200
As Required
EVEN
As Required
Remote
DISABLED
As Required
0
As Required
Notes
Sets the protocol used to
communicate on the
standard RS485 connection.
The baud rate set on all of
the relays connected to the
control system must be the
same as the one set on the
master device.
The parity set on all of the
relays connected to the
control system must be the
same and in accordance
with the master device.
Setting is only visible when
COM1 Protocol is set to
DNP3
Setting is only visible when
DNP3 Unsolicited Events
set to Enabled.
Chapter 4 Page 7 of 54
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