S7-1200 Fail-Safe Cpus - Siemens SIMATIC S7 Functional Safety Manual

Product overview

1.3 S7-1200 Fail-Safe CPUs

1.3 S7-1200 Fail-Safe CPUs
The fail-safe CPU executes your safety program along with standard applications programs.
Communication between the fail-safe CPU and the fail-safe signal modules is verified using
the PROFIsafe protocol.
Safety program
You can create a safety program using the program editor. You can program fail-safe
function blocks (FB) and functions (FC) in the Function Block Diagram (FBD) or Ladder
Logic (LAD) programming languages and create fail-safe data blocks (DB).
The fail-safe system performs a dual execution using coded processing. The fail-safe system
automatically performs safety checks and inserts additional fail-safe logic for error detection
and error response when the safety program compilation occurs. This ensures the detection
of failures and faults and appropriate execution of reactions to maintain the fail-safe system
in the safe state or bring it to a safe state.
In addition to the safety program, you can run a standard user program on the fail-safe CPU.
A standard program can coexist with a safety program in a fail-safe CPU. The fail-safe CPU
protects the safety-related data of the safety program from the unintentional effects of the
data of the standard user program.
You cannot put an S7-1200 Fail-Safe system that provides safety-related functions into
operation after installation or modification until after you successfully commission the
safety-related functionality.
Death or serious personal injury and damage to machines and equipment may result if
proper precautions are not taken.
An S7-1200 Fail-Safe system that provides both safety-related functions and standard (non
safety-related) functions must not be put into operation in order to use the standard
functions before you successfully commission the safety-related functions, even if all fail-
safe signal modules go to the error state and thus remain safe.
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WARNING
S7-1200 Functional Safety Manual
Manual, 02/2015, A5E03470344-AA