Safety Instructions
In the controller organizer, you can recognize safety programs by the red bar 
that is incorporated into the icons. The red bar indicates the program will execute in safety memory.
that is incorporated into the icons. The red bar indicates the program will execute in safety memory.The buttons for instructions that function as part of a safety program, or are supported by a safety program, have a red triangle 
in the right corner of each button.
in the right corner of each button.System Dependencies
The safety application instructions depend on the safety I/O modules, controller operating system, and the ladder logic to perform portions of the safety functions.
Available Instructions
Ladder Diagram
These safety instructions were introduced in
Logix Designer
version 17. Rockwell Automation
recommends using these instructions for logic in safety systems.These legacy instructions are supported but in most cases are not as efficient as the instructions introduced in
Logix Designer
version 17.Safety application instructions are intended for use within a safety system that has a controller and I/O modules. These instructions are intended for Safety Integrity Level (SIL) 3, PLe/Category (CAT) 4 applications.
If you want to | Use this instruction |
Monitor dual-input safety devices whose main purpose is to provide a stop function, such as an E-stop, light curtain, or gate switch. | DCS |
Monitor dual-input safety devices whose main purpose is to provide a stop function, such as an E-stop, light curtain, or gate switch. It includes the added capability of initiating a functional test of the stop device. | DCST |
Monitors dual-input safety devices whose main purpose is to stop a function, such as an E-stop, light curtain, or gate switch. It includes the added capability of initiating a functional test of the stop device and can monitor a feedback signal from a safety device and issue a lock request to a safety device. | DCSTL |
Monitor dual-input safety devices whose main purpose is to provide a stop function, such as an E-stop, light curtain, or gate switch. It includes the added capability of initiating a functional test of the stop device and the ability to mute the safety device. | DCSTM |
Energize dual-input safety devices whose main function is to start a machine safely, for example an enable pendant. | DCSRT |
Monitor dual-input safety devices. | DCM |
Indicate that a safety mat is unoccupied. | SMAT |
Provide temporary, automatic disabling of the protective function of a light curtain, using two muting sensors arranged asymmetrically. | TSAM |
Provide temporary, automatic disabling of the protective function of a light curtain, using two muting sensors arranged symmetrically. | TSSM |
Provide temporary, automatic disabling of the protective function of a light curtain, using four sensors arranged sequentially before and after the light curtain’s sensing field. | FSBM |
Monitor two diverse safety inputs, one from a right-hand push button and one from a left-hand push button, to control a single output. | THRSe |
Control and monitor redundant outputs. | CROUT |
Monitor two analog input channels originating from an analog input module. (Integer version) | DCA |
Monitor two analog input channels originating from an analog input module. (Floating Point version) | DCAF |
Migrate to preferred instructions
If you are using
Logix Designer
version 17 or later, use these newer, preferred instructions in place of the corresponding legacy instructions.Function Block
Not available
Structured Text
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