16 Rockwell Automation Publication 1756-RM012B-EN-P - April 2018
Chapter 2 GuardLogix Controller System
Primary Controller
The primary controller is the processor that performs standard and safety
control functions and communicates with the safety partner for safety-related
functions in the GuardLogix control system. The primary controller consists of
a central processor, I/O interface, and memory.
Safety Partner
To satisfy SIL 3 requirements, you must install a ControlLogix 558SP safety
partner in the slot immediately to the right of the primary controller. The
safety partner is a co-processor that provides 1oo2 architecture for safety-
related functions in the system. The 1oo2 system does not run degraded. If the
two processors disagree, or cannot communicate with each other, the result is a
major non-recoverable controller fault. For information on how to respond to
this situation, see article 63983
in the Rockwell Automation® Knowledgebase.
For SIL 2 requirements, do not install a safety partner.
The primary controller configures the safety partner. Only one download of
the user program to the primary controller is required. The primary controller
controls the operating mode of the safety partner.
Chassis
The chassis provides the physical connections between modules and the 1756
GuardLogix system. Any failure, though unlikely, would be detected as a failure
by one or more of the active components of the system. Therefore, the chassis is
not relevant to the safety discussion.
Power Supply
No extra configuration or wiring is required for SIL 2 or SIL 3 operation of the
ControlLogix power supplies. Any failure would be detected as a failure by one
or more of the active components of the GuardLogix system. Therefore, the
power supply is not relevant to the safety discussion.
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