Additional (Optional) Rs485 Connections; Additional (Optional) Rs232 Connections; Figure 6.4-1 Rs485 Data Comms Connections Between Relays; Figure 6.5-1 Rs232 Data Comms Pin Connections - Siemens Argus 7SR21 Installation Manual

6.4

Additional (Optional) RS485 Connections

The additional (optional) RS485 communication port is located at 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 the A and
B by fitting an external wire loop between terminals 18 and 20 on the power supply module.
To
Control
System
Rear terminals
To
Control
System
RS485

Figure 6.4-1 RS485 Data Comms Connections Between Relays

6.5

Additional (Optional) RS232 Connections

The additional (optional) RS232 (9 pin plug) (DTE) communication port is located at the rear of the relay and can
be connected using a suitable RS232 cable.
Where there is a requirement for multi-drop RS232 connection, a suitable device to facilitate this should be
obtained.
©2010 Siemens Protection Devices Limited
14
16
18
RS485 Screened
twisted pair
RS 485 Twisted pair screened Cable
Pin
1
2
3
4
5
6
7
8
9

Figure 6.5-1 RS232 Data Comms Pin Connections

7SR21 & 7SR22 Argus Installation Guide
14
16
18
RS485 Screened
twisted pair
RS485
Relay Function
Not Connected
Receive Data (RXD)
Transmit Data (TXD)
Input Supply +5 V
Signal Ground (GND)
Input Supply +5 V
Linked to 8 (volts free)
Linked to 7 (volts free)
Output Supply +5 V 50mA
Ext Wire loop to
Include line
terminating Res
14
16
18
20
Rear terminals
RS485
Chapter 5 Page 16 of 22