Rockwell Automation 1791DS-IBxxxx Guard I/O DeviceNet Safety Modules - Manual (Page 83)

Rockwell Automation Publication 1791DS-UM001J-EN-P - May 2013 83
Configure Modules in RSNetWorx for DeviceNet Software Chapter 6
3. From the General tab, change these values.
a. In the Name box, type a unique name.
b. In the Description box, type a description (optional).
c. In the Address box, enter the DeviceNet node number.
This DeviceNet node number and the switches on the actual module
must match.
4. Click the Safety tab.
On the Safety tab, you set the safety network number (SNN) and the
configuration signature.
Safety Network Number (SNN)
The purpose of the safety network number (SNN) is to make sure that every
module in a system can be uniquely identified.
For example, assume there are two identical GuardLogix control systems—
System A and System B—that are connected to a common Ethernet network.
System A and System B have three DeviceNet networks with assorted standard
and safety I/O modules. In systems like this, modules can have the same node
number, but if each DeviceNet network has a unique SNN, each node will not
have the same SNN and node number combination.
Another example of the usage of SNNs is when 1756-DNB modules are in the
same chassis and the DeviceNet cables are inadvertently disconnected. If the
cables are reattached incorrectly, the connection in the safety modules are broken
because each 1756-DNB module is now connected to devices with different
SNNs.
We suggest that all safety modules on a network have the same SNN, to make
documentation easier. During configuration, the Logix Designer application