Logix SIS Architecture
Logix SIS architecture is defined by these characteristics:
- Redundant safety controllers and other hardware components that control safety-related functions.
- Concurrent execution of the safety task on primary and secondary qualified safety controllers.
- Dynamic transitions between a 1oo1 and 1oo2 safety architecture during these events:
- Qualification of the redundant chassis pair—Once safety controllers are qualified and synchronized in a redundant chassis pair, the system transitions from a 1oo1 to 1oo2 architecture. In this operational state, both controllers cross-check the safety task results and either controller can respond to a safety demand.
- Loss of redundancy—If the system loses redundancy, the system transitions from a 1oo2 to a 1oo1 architecture. In this operational state, one of the redundant controllers no longer participates in the safety function while the other continues to execute the safety function alone.
- Concurrent communication with remoteFLEX 5000®safety I/O modules.
Logix SIS Architecture
To operate as described, Logix SIS requires these configuration settings in the controller properties:
- Redundancy must be enabled on the Redundancy tab.
- The safety level on the Safety tab must be set appropriately for the firmware revision you are using as shown below. In firmware revision 38, the safety level is static and cannot be changed when the controller is configured for Logix SIS.
Firmware Revision | Safety Level |
|---|---|
38 or later | SIL3/PLe when synchronized or disqualified within MRT; SIL2/PLd when disqualified |
37 | SIL2/PLd |
IMPORTANT:
- With firmware revision 38 or later, the GSV SafetySILConfiguration attribute always shows a SIL 3 value even when your system complies with a SIL 2 safety function.
- With firmware revision 37, the GSV SafetySILConfiguration attribute always shows a SIL 2 value even when your system complies with a SIL 3 safety function. A SIL2/PLd safety level is the required configuration for controllers that are enabled for redundancy.
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