Rockwell Automation Publication 1756-RM093J-EN-P - April 2018 19
Safety Integrity Level (SIL) Concept Chapter 1
Safety Task Period and Safety Task Watchdog
The safety task period is the interval at which the safety task executes.
The safety task watchdog time is the maximum permissible time for safety task
processing. If safety task processing time exceeds the safety task watchdog time, a
non-recoverable safety fault occurs in the controller and outputs transition to the
safe state (off) automatically.
You define the safety task watchdog time, which must be less than or equal to the
safety task period.
The safety task watchdog time is set in the task properties window of
RSLogix 5000 software. This value can be modified online, regardless of
controller mode, but it cannot be changed when the controller is safety-locked or
once a safety task signature is created.
Contact Information if Device
Failure Occurs
If you experience a failure with any SIL 3-certified device, contact your local
Rockwell Automation distributor to initiate the following actions:
• You can return the device to Rockwell Automation so the failure is
appropriately logged for the catalog number affected and a record is made
of the failure.
• You can request a failure analysis (if necessary) to try to determine the
cause of the failure.
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