Network Protocol - ABB ETL600 Instruction Manual

ABB Switzerland Ltd
Fig. 4-6
In the common situation, where several links are connected in tandem
(chain of links), all terminals can be reached from either side of the
chain by connecting the management ports of the terminals together
via RS485 bus as shown in Fig. 4-7.
Substation A
HMI600
RS232-
connection
Substation D
RS485-
bus
Fig. 4-7
T-offs in substations can be handled by connecting the management
ports of the involved terminals via RS-232/RS-485 converters as
shown in Fig. 4-5.
4.5.3.

Network protocol

The network protocol used by the ETL600 terminals is connectionless.
This means that all messages circulating in the network are routed to
all terminals attached to the network. Only the addressed terminal will
execute the commands contained in the message and generate an
answer. Closed loops are not allowed in the network. In the example of
Fig. 4-8, a closed loop exists between substations A and C. All
messages exchanged between substations A and C will be transmitted
over a data channel of 9'600 bps as well as over the 100 bps EOC
channel of the PLC link between terminals A3 and C3. Unless the
EOC of the PLC link A3-C3 is disabled for network management by
proper configuration via HMI600 (by not checking the box Network
management: EOC enabled in the HMI600 dialog box Configuration
/ System / Channel settings), the network will not operate properly.
Thus the EOC must be disabled for network management in this case.
4-12
1KHW001489-EN
Substation A
HMI600
RS232-
connection
ETL600
Embedded operation channel
EOC of
PLC link
ETL600
EOC of
PLC link
ETL600
Chain of ETL600 links
November 2005
Substation B
EOC of
PLC link
ETL600
Substation B
RS485-
bus
ETL600
Substation C
RS485-
bus
ETL600
User Interface Program
ETL600
ETL600
EOC of
PLC link
ETL600