Allen-Bradley 1756-L6 Series, Reference Manual, Page: 19 / 134

Rockwell Automation Publication 1756-RM001I-EN-P - May 2012 19
SIL Policy Chapter 1
Figure 6 shows a typical duplex SIL loop. The figure also shows the following:
• Overall safety loop
• ControlLogix portion of the overall safety loop
• How other devices (for example, HMI) connect to the loop, while
operating outside the loop
Duplex (fault-tolerant) System Configuration
This configuration of the ControlLogix system uses fully-redundant controllers,
communication modules, and remote I/O devices to achieve enhanced
availability.
Figure 7 - Duplex System EtherNet/IP Configuration
ControlLogix Chassis
EtherNet/IP
PRI COM OK
I/O Chassis A
I/O Chassis B
ST
ST
DIAGNOSTIC
O
K
0 1 2 3 4 5 6 7
8 9 10 1112 13 14 15
DC INTPUT
ST
ST
DIAGNOSTIC
O
K
0 1 2 3 4 5 6 7
8 9 10 1112 13 14 15
DC INTPUT ANALOG INTPUT
CAL
OK
ANALOG INTPUT
CAL
OK
ST
ST
DIAGNOSTIC
O
K 0 1 2 3 4 5 6 7
8 9 10 1112 13 14 15
DC OUTPUT
ST
ST
DIAGNOSTIC
O
K 0 1 2 3 4 5 6 7
8 9 10 1112 13 14 15
DC OUTPUT
ST
ST
DIAGNOSTIC
O
K 0 1 2 3 4 5 6 7
8 9 10 1112 13 14 15
DC INTPUT
ST
ST
DIAGNOSTIC
O
K 0 1 2 3 4 5 6 7
8 9 10 1112 13 14 15
DC INTPUT ANALOG INTPUT
CAL
OK
ANALOG INTPUT
CAL
OK
ST
ST
DIAGNOSTIC
O
K 0 1 2 3 4 5 6 7
8 9 10 1112 13 14 15
DC OUTPUT
ST
ST
DIAGNOSTIC
O
K 0 1 2 3 4 5 6 7
8 9 10 1112 13 14 15
DC OUTPUT
Secondary Chassis
PRI COM OK
Field Device Field Device Field Device
Analog Input
Termination
Board Digital Input
Termination
Board Digital Output
Termination Board
SIL 2-certified ControlLogix Safety Loop
Allen-Bradley Motors