Rockwell Automation Publication 1715-RM001A-EN-P - June 2019
13
Chapter
2
Features of the ControlLogix SIL 2 System
Overview
The ControlLogix® controller consists of a central processor, I/O interfaces, and
memory.
The ControlLogix controller can be a simplex (Single Chassis) or redundant
configuration (Dual Chassis with RM). This makes no impact on the SIL
calculation of the safety function. This adds availability to the safety function,
but no change to safety. In a Duplex configuration, the system switches from a
1oo1 controller to another 1oo1 controller if there is a fault in the controller
chassis.
Operating Modes
A three-position keyswitch on the front of the controller governs ControlLogix
system operational modes. The following modes are available:
• Run – This is known as Hard Run. No online changes are possible
• Program – This stops the execution of the application code and allow
online changes
• Remote - This software-enabled mode can be Program or Run. In this
mode, you can make online changes while the application is running but
the change requires a confirmation. You can also put the controller into
program mode via a command. Because of these functions, it is required
for the controller to be in Hard Run when operating in Safety Mode.
Making any edit always involves following your own MOC (Management of
Change) procedures. There must be a validation before putting the changed code
into service. Online edits are the most risky method of doing this and are not
recommended.
IMPORTANT
The keyswitch must be in the RUN position to be SIL 2 certified. If you put the
keyswitch into the REMOTE position to make an online edit, you are not in
safety mode. When you are finished with the online edit, you must put the
keyswitch into RUN position and remove the key.
