Rockwell Automation AADvance Controller Solutions Handbook - Manual (Page 57)

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Document: 553631
(ICSTT-RM447J_EN_P) Issue: 09:
2-7
SIL3 Fail-safe I/O, Fault Tolerant Processor
A SIL3, fail-safe I/O with a fault tolerant processor architecture has a simplex input and
output arrangement with dual or triple processor modules. The dual processor
modules operate in 1oo2D under no fault conditions and degrade to 1oo1D on
detection of the first fault in either module. When there are faults on both modules
the configuration will fail-safe.
If required you can configure triple processor modules as a variation of this SIL3
architecture. Using this arrangement the processor modules operate in 2oo3D under
no fault conditions and 1oo2D on the detection of the first fault in any module. They
degrade to 1oo1D on the detection of faults in any two modules, and will fail-safe
when there are faults on all three modules.