Rockwell Automation 1794 FLEX I/O System with ControlLogix for SIL2 - Manual (Page 6)

Publication 1794-RM001G-EN-P - December 2011
1-2 SIL Policy
SIL2 Certification Figure 1.1 shows a typical SIL loop, including:
• the overall safety loop
• the ControlLogix/FLEX I/O portion of the overall safety loop
• how other devices (for example, HMI) connect to the loop, while
operating outside the loop
Figure 1.1
Plant-wide Ethernet/Serial
ControlNet
SIL2-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). For more information, see publication 1756-RM001 .
E
N
B
C
N
B
To other safety related
ControlLogix or FLEX I/O
remote I/O chassis
Overall Safety Loop
Actuator
Actuator
1794 FLEX I/O
Input
Device
DI1
DO2
DO1
DI2
ControlNet
Input
Device
To other safety related
ControlLogix or FLEX I/O
remote I/O chassis
See Figures 3.1 and 3.5 for details.
1
Note 1: Multiple 1756-CNB or -CNBR modules can be installed into the chassis as needed.
Other configurations are possible as long as they are SIL2 approved.
+V
Note 2: Two adapters are required for meeting SIL2 as shown in the figure.
The adapters can be either ControlNet or Ethernet and must be from the list of approved products.