228 Rockwell Automation Publication 1715-UM001J-EN-P - December 2020
Chapter 8 Using SIL 2 Add-On Instructions with 1715 Redundant I/O Modules
2. Configure SIL 2=Yes in the module configuration and click Apply to
create the required module defined data types.
3. Import the new Add-On Instructions.
Create a Periodic Task for
SIL 2 Safety Functions
We recommend that your user application contains one SIL task that is
composed of programs and routines that contain all logic for the SIL 2-rated
safety functions. This task must be the top-priority task of the controller, and
the user-defined watchdog must be set to accommodate the SIL task.
This task must be separate from all logic for the non-SIL 2-rated functions.
Follow these steps to create the SIL 2 periodic task.
1. In the Controller Organizer, right-click the Tasks folder and choose New
Task.
2. Name the Task (SIL 2, for example).
3. Select the Type ‘Periodic’.
1715 SIL 2 Periodic Task ‘Period’ Configuration
The following are recommendations to configure the periodic task ‘period’ for
SIL 2 applications. Set the period to the minimum 1715 SIL 2 module RPI
divided by 2. For example, if the default RPIs are used.
1. Make the period 60/2 = 30 ms.
Table 45 - Module Default RPIs
1715 Module RPI
Adapters 180 ms
Digital modules 60 ms (lowest)
Analog modules 120 ms
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