Rockwell Automation 1791DS-IBxxxx Guard I/O DeviceNet Safety Modules - Manual (Page 110)

110 Rockwell Automation Publication 1791DS-UM001J-EN-P - May 2013
Chapter 6 Configure Modules in RSNetWorx for DeviceNet Software
If you see the following message after attempting to download, the likely scenario
is that the 1791DS module was previously owned by a different safety controller.
You must reset the owner before the 1791DS module will make a new safety
connection.
To reset the 1791DS module, right-click the module and choose Reset Safety
Device.
The Reset Safety Device dialog box appears.
Check Password and Safety Network Number so that the 1791DS module is
totally reset. Click Reset.