Allen-Bradley 1756-L6 Series, Reference Manual, Page: 18 / 134

18 Rockwell Automation Publication 1756-RM001I-EN-P - May 2012
Chapter 1 SIL Policy
Duplex Logic Solver Configurations
In duplex configurations, redundant system components are used to increase the
availability of the control system. The modules in the redundant controller
chassis include redundancy modules and network communication modules for
redundant communication, as well as the ControlLogix controllers.
SIL 2 I/O modules in the safety loop must meet the requirements specified in
Chapter 5 , ControlLogix I/O Modules .
Figure 6 - Typical SIL Loop with Controller Chassis Redundancy
Plant-wide Ethernet/Serial
ControlNet
SIL 2-certified ControlLogix components’ portion of the overall safety loop.
Programming Software
For SIL applications, a programming
terminal is not normally connected.
HMI
For Diagnostics and Visualization (read-only access to controllers in the safety
loop).
Sensor Actuator
ControlNet
IMPORTANT : You can also access a
remote I/O chassis via an EtherNet/IP
network if you use ControlLogix
Enhanced Redundancy System,
Revision 19.52 or later .
To nonsafety-related systems outside the ControlLogix portion of the SIL
2-certified loop.
To other safety
related
ControlLogix
and remote
I/O chassis.
Overall Safety Loop
I/O
Primary Chassis
Secondary Chassis
Remote I/O Chassis
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IMPORTANT
The redundant (duplex) ControlLogix system in Figure 6 is fault-tolerant for
the devices in the primary/secondary controller chassis.