Rockwell Automation 1715-OF8I Redundant I/O System User Manual - Manual (Page 208)

208 Rockwell Automation Publication 1715-UM001C-EN-P - March 2014
Chapter 6 1715 Redundant I/O System in SIL 2 Safety Applications
Requirements for
ControlLogix-based SIL 2
Applications
Add-On Instructions
The Add-On Instructions provide a mechanism to verify the validity of data
transferred between the ControlLogix controller and the 1715 adapter. When
you use the Add-On Instructions, the sender of the data adds check data to the
produced data. The receiver of the data uses the check data to verify the integrity
of the consumed data.
Connection Reaction Time Limit
The Connection Reaction Time Limit (CRTL) setting defines the maximum
time that the connection can operate with old data, before substituting the
configured safe state values. If the CRTL expires, the receiver requires a SIL 2
Reset before valid data is provided again.
For an input module, if the CRTL expires before the Add-On Instruction detects
valid data, the value of the affected input assembly transitions to the configured
safe state value. A SIL 2 reset is required before inputs transition from the safe
state to field values.
For an output module, if the CRTL expires before the 1715 firmware detects that
valid output data is received from the Logix controller the output data transitions
to the configured safe state values. In this case, a SIL 2 Reset is required before
outputs can be re-energized.
Using the 1715 Adapter in
SIL 2 Applications
The 1715-AENTR adapter performs the following functions:
• External communication with the controller via an Ethernet network
• Communication with I/O modules, such as receiving input values, sending
output values, and coordinating diagnostics
• Enforcement of the output CRTL on data received from a ControlLogix
controller
For high availability, use two 1715-AENTR adapters in simplex and duplex SIL 2
applications.
IMPORTANT SIL 1 applications must use the wiring and measures defined for SIL 2
applications. Energize-to-action requires line monitoring for any SIL
application.
IMPORTANT To meet SIL 2 application requirements in a ControlLogix system, you must use
the 1715 Add-On Instructions described in
Chapter 7 .