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SNN Formats
SNNs used by the system are 6-byte hexadecimal numbers. SNNs can be set
and viewed in one of two formats:
• Time-based
• Manual
Time-based SNN Format and Assignment
When the time-based format is selected, the SNN represents a localized date
and time.
Figure 11 - SNN Formats
The assignment of time-based SNNs is automatic when you create a
GuardLogix safety controller project or add EtherNet/IP by changing the IP
mode (Compact GuardLogix 5380 only) or controller type. Time-based SNNs
generated by the software are always unique to the project, whether generated
by project creation or IP mode change. Devices that are created directly under
the controller port default to having the same SNN as that port on the
controller.
IMPORTANT If you have a network diagram for your application (for example,
you must edit the SNNs of the controller to match your network diagram. We
recommend that you edit the SNNs before adding devices to the I/O
Configuration in Controller Organizer.
New CIP Safety I/O devices added to ports under an adapter (as opposed to
the controller itself ) follow similar rules.
• If no other device under the port uses an SNN, a time-based SNN is
automatically assigned.
• Otherwise, the device is assigned the same SNN as the first device in
address order that has an SNN.
Rockwell Automation Publication 1756-RM012B-EN-P - April 2018
CIP Safety and Safety Network Numbers
Chapter 4
Figure
9),
33
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