User's Manual

Model CH45
EIA 422 or 485
2-7
2.2 LOOP OPERATION - MASTER/SLAVE CONFIGURATION
NOTE
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 either an Optical Bus or
Optical Star configuration.
This configuration supports a system which requires more than two IEDs to be communicating. In a
Master/Slave loop system, one IED acts as a Master at all times and addresses or "polls" each of the
other connected IEDs individually. Each Slave receives the same transmission from the Master IED but
only responds when it recognizes its address in the polling message.
2413
Master
T+
T-
R+ R-
REP
OFF
2413
Typical Slave
T+
T-
R+R-
REP
OFF
2413
Typical Slave
T+
T-
R+R-
REP
OFF
2413
Last Slave
T+
T-
R+R-
REP
OFF
FIGURE 12. Master/Slave Loop Configuration