Siemens ST PCS 7 manual 10/26, Safety functions

© Siemens AG 2008

Automation systems

Safety-related automation systems

■Function ■Options

Safety functions

The safety functions of an application are implemented by the safety-related program executed in the CPU of the F/FH systems together with the safety-related F-modules of the ET 200 distrib- uted I/O systems or directly by failsafe transmitters connected via the fieldbus.

The PROFIsafe profile is used for the safe PROFIBUS DP com- munication between CPU and process I/O. PROFIsafe expands the message frames by additional information with which the PROFIsafe communications partners can recognize and com- pensate transmission errors such as delays, incorrect se- quences, repetitions, losses, faulty addressing or data falsifica- tion.

Standard modules can be used in F/FH systems in addition to safety-related F-modules - mixed in a remote I/O station or in separate stations, in a common PROFIBUS segment or in sepa- rate PROFIBUS segments. Basic process control (BPCS) appli- cations and safety applications can be automated in such mixed configurations with one and the same system and configured with uniform standard tools.

One CPU processes BPCS and safety functions in parallel. Mutual interference during processing is prevented by ensuring that the BPCS programs and the safety-related programs are kept strictly separate and that the data exchange is by means of special conversion function blocks. The safety functions are pro- cessed twice in different sections of a CPU by means of redun- dant, diverse instruction processing. Potential errors are de- tected by the system during the subsequent comparison of results.

The S7 F Systems engineering tool as a component of the SIMATIC Manager allows parameterization of the F/FH systems and the safety-related F-modules from the ET 200 series. It sup- ports configuration by means of functions for:

• Comparison of safety-related F-programs

10 • Recognition of changes in the F-program using the checksum

•Separation of safety-related and standard functions. Access to the F-functions can be password-protected.

The F-block library integrated in S7 F Systems contains pre- defined function blocks for generation of safety-related applica- tions with the CFC or the SIMATIC Safety Matrix based on it. The certified F-blocks are extremely robust and intercept program- ming errors such as division by zero or out-of-range values. They avoid the need for diverse programming tasks for detecting and reacting to errors.

Ordering information

An AS 412H, AS 414H or AS 417H system is required as the hardware for a safety-related automation system.

The following H systems can be used depending on the type and structure of the safety-related automation system:

•For single-channel AS 412F, AS 414F or AS 417F safety-re- lated systems: one each of AS 412-3-1H, AS 414-4-1H or AS 417-4-1H

•For fault-tolerant and safety-related AS 412FH, AS 414FH or AS 417FH systems:

-With both subsystems in one rack: one each of AS 412-3-2H, AS 414-4-2H or AS 417-4-2H

-With the two subsystems in different racks: two each of AS 412-3-1H, AS 414-4-1H or AS 417-4-1H

You require the following components in addition:

•S7 F Systems

F programming tool with F block library for programming safety-related user programs on the engineering system (see Chapter "Engineering system")

•F Runtime license

For processing safety-related user programs, for one AS 412F/FH, AS 414F/FH or AS 417F/FH system

•Option: SIMATIC Safety Matrix

The convenient safety lifecycle tool for configuration of opera- tion and servicing (see Chapter "Engineering system")

10/26

Siemens ST PCS 7 · Update November 2008