How SNNs Get to Safety Devices
Most
CIP Safety™
I/O modules in the factory default state accept an SNN that is assigned by the controller that owns that module. The SNN value that the programming software automatically adopts for the connection of that module is accepted when the controller opens the initial connection to the module.
IMPORTANT:
CIP Safety™
I/O modules retain their UNID (SNN + node) once it has been assigned and must be reset before they can be reused with another value.Some devices, such as another safety controller in the I/O tree, receive their SNN configuration from a programming workstation. For these devices, you must manually configure the connection to use the same SNN that has been programmed into that device if the programming software did not automatically assign the correct SNN.
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