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2.2
LOOP OPERATION - MASTER/SLAVE CONFIGURATION
Before constructing a loop network, be sure that the software protocol of the Master is capable of managing
the receipt of its own, echoed transmission. If it cannot, then use Point-to-Point configurations only between
devices in an "optical bus" network approach.
This configuration supports a system that requires more than two IED's to be communicating.
Master/Slave loop system, one IED acts as a Master at all times and addresses or "polls" each of the other
connected IED's individually.
responds when it recognizes its address in the polling message.
3
T
The Master must have its Repeat Switch in the "OFF" position. When it transmits a request out its T optical
port, it will receive the echo of its request at its R optical port. This request has gone around the loop, and has
been repeated by each Slave in the loop. However, the Master does not repeat (re-transmit) any of these
received signals optically back around the loop, because its Repeat Switch is in the "OFF" position.
Each Slave receives the same transmission from the Master IED but only
ON
OFF
5
2
R
COM
Slave
FIGURE 8. Master/Slave Loop Configuration
NOTE
M aster
T
R
COM
2
5
3
ON
OFF
3
5
2
T
R
COM
Slave
2-6
Models 5843, 5844, 5843S and 5844S
ON
OFF
3
5
2
T
R
COM
Slave
RS232 or TTL
In a
ON
OFF
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