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Rules Governing the Use of the S5-115F
10.7.6 Loadable Function Blocks
Frequently recurring or particularly complex program sections (e.g. signalling or arithmetic
functions) are programmed in function blocks. These can be assigned parameters and have an
extended operation set (e.g. jump operations within a block).
The loadable function blocks are subdivided into
•
User-written function blocks
•
Standard function blocks
User-Written Function Blocks
Function blocks generated by the user - like any other block - must be tested by the inspector.
The minimum requirements of the test are a discussion of the function, functional tests with an
examination of possible error states and a code analysis.
Standard Function Blocks
In the S5-115F, standard function blocks may be used only when they have been prototype-tested.
The standard FBs for the S5-115F implement the same functions as the standard FBs for the
SIMATIC S5 U-range controllers, but have been adapted to the safety requirements. You will find
an overview of the standard function blocks which can be used in the S5-115F in Catalog ST 57.
There are reaction-free and failsafe standard FBs. Only failsafe standard FBs may be used to form
signals relevant to the system's failsafety. When assigning parameters to the blocks, note that
output parameters can only be failsafe if all the input parameters are failsafe.
All standard FBs are identified by a library number which, in conjunction with other measures,
protect the blocks against falsifications caused by transfer errors or disk errors.
Note the following when using loadable standard FBs:
•
In the safety mode, the operating system checks all standard FBs for integrity
•
Standard FBs for the SIMATIC S5 U-range controllers are not allowed, and are rejected in the
safety mode
•
The authorized inspector's examination of the standard FBs limits itself to
- a comparison of the library number with the one specified in the report
- checking for proper use of the standard FBs
- checking the FB calls for correctness and checking the parameter initialization routine for
the FBs as per the block description
- making sure that the provisions laid down in the report or the requirements of the
prototype test have been upheld
Note
If you use standard FBs, you may only use flag words FW 200 to FW 254 in your user
program if you save the flag area used before calling the standard FB and retrieve it
when the block has been processed.
10-14
S5-115F Manual
EWA 4NEB 811 6148-02
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