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Digital Module Operation in a Control System
Chapter 1
Overall System Safety Function
The type approval, certification, and suitability levels for Compact 5000 I/O
safety modules describe a system with an overall system safety function of
SIL 3. However, you are not required to use Compact 5000 I/O safety
modules in safety applications with an overall system safety function of SIL 3.
For example, Compact GuardLogix 5380 controllers are suitable for use in
safety applications that are rated up to, and including, SIL CL2, PLd, Cat. 3 as
defined in IEC 61508, IEC 61511, IEC 62061, and ISO 13849-1.
In this case, the overall system safety function is SIL 2. You can use Compact
5000 I/O safety modules in such an application.
GuardLogix 5580 controllers, when used with a safety partner are suitable for
use in SIL 3 safety applications. You can use Compact 5000 I/O safety
modules as remote I/O modules in such an application.
For more information on the suitability level of Logix 5000 safety controllers,
see the GuardLogix 5580 and Compact GuardLogix 5380 Controller Systems
Safety Reference Manual, publication 1756-RM012.
Single-channel or Dual-channel Mode
You can use Compact 5000 I/O safety modules in single-channel mode or
dual-channel configuration. The configuration affects the safety application
suitability level for a module.
In single-channel mode, the signal status on one channel is evaluated. Based on
that status, safety input data and safety input status can be off or on.
In dual-channel mode, the consistency between the signal status on two
channels is evaluated. Based on the status on both channels, safety input data
and safety input status can be off or on.
You use safety instructions in the safety controller ladder logic with two single
channels, that is, one even and one odd.
We recommend that, if you use dual channel safety instructions, for example,
the Dual Channel Input Stop (DCS) instruction, in the Safety Task, you
configure the channels for single-channel mode.
Rockwell Automation Publication 5069-UM004A-EN-P - April 2019
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