Chapter 4) 7SR23 DAD Data Communications
©2013 Siemens Protection Devices Limited
Chapter 4 Page 7 of 54
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
Range
Default
Setting
Notes
COM1-RS485 Protocol
OFF, IEC60870-5-103,
MODBUS-RTU, DNP3.0
IEC60870-5-
103
As Required
Sets the protocol used to
communicate on the
standard RS485 connection.
COM1-RS485 Baud
Rate
75 110 150 300 600 1200
2400 4800 9600 19200
38400
19200
As Required
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.
COM1-RS485 Parity
NONE, ODD, EVEN
EVEN
As Required
The parity set on all of the
relays connected to the
control system must be the
same and in accordance
with the master device.
COM1-RS485 Mode
Local, Local or Remote,
Remote
Remote
Unsolicited Mode
DISABLED ENABLED
DISABLED As
Required
Setting is only visible when
COM1 Protocol is set to
DNP3
Destination Address
0 … 65520
0
As Required
Setting is only visible when
DNP3 Unsolicited Events
set to Enabled.
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Figure 2-2
Communication to Multiple Devices using RS485 (Standard Port)
Summary of Contents for 7SR23 DAD
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