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1 Overview
NX-series Safety Control Unit User’s Manual (Z930)
1-4 Exchanging Signals
between Units
1
1-4-1 Relationship between Units and Types of Communications
The following table summarizes the relationship described above.
Relationship between Master and Slaves during Safety Process Data Commu-
nications
The following figure shows the safety master/slave relationship during safety process data commu-
nications.
The Safety CPU Unit performs safety process data communications with the Safety I/O Units on the
same Slave Terminal, or the Safety I/O Units on another Slave Terminal on the EtherCAT network.
In this relationship, the Safety CPU Unit operates as the master in the safety process data commu-
nications. Meanwhile, the Safety I/O Units operate as slaves in the safety process data communica-
tions.
Units
Communications type Typical application
Master Slaves
Safety CPU Unit Safety I/O Units Safety process data communica-
tions (Section (A) in the above
figure)
Safety control signals from the
Safety CPU Unit.
Standard CPU Unit Safety CPU Unit Standard process data commu-
nications (Section (B) in the
above figure.)
Monitoring and operation prepa-
ration commands for the Safety
CPU Unit and Safety I/O Units
from the Standard CPU Unit
Safety I/O Units Standard process data commu-
nications (Section (C) in the
above figure.)
The Standard CPU Unit receives
the status information from the
Safety I/O Units.
Relationships between Master and Slaves during EtherCAT Network
Communications
S S
S
S
S
M
M
Safety
CPU
Unit
NJ/NX-series
CPU Unit
Coupler
Unit
Safety Output
Safety Input
Coupler
Unit
Safety Output
Safety Input
Safety master
Safety control system
Safety slave
Safety process data communications
EtherCAT
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