Functional description

The safety-related SF_RecipeDeleteDataSet function block is part of a safety library which provides function blocks for the applicative recipe handling of the Safety PLC.

The SF_RecipeDeleteDataSet FB can delete a specified data set in a recipe file by overwriting each value in the file section with the value 0.

The FB is therefore functionally (especially with regard to its validation routines) more comparable to the SF_RecipeWrite block than to the SF_RecipeDeleteFile FB.

After deleting the specified data set by overwriting its content with 0 values, the modified recipe file is updated with the project CRC of the current project and the serial number of the Safety PLC.

After completing the data set delete operation, the Done output is set to SAFETRUE.

Recognition of incorrect/invalid data set deletion operations

The function block implements measures to detect if an invalid file or data set ID is applied to an FB input. Furthermore, multiple delete requests for the same data set by several instances of the SF_RecipeDeleteDataSet function block are detected and prevented.

Allowed but potentially unwanted multiple accesses

Other simultaneous accesses by several recipe function blocks may be not considered as an error but should nevertheless either be prevented by structuring the safety application accordingly or, if they are necessary, verified carefully by means of a function test.
Examples for such generally allowed but potentially critical simultaneous accesses are:

Simultaneous read and "file delete" operations within one cycle.
Simultaneous write and "file delete" operations within one cycle.

Further Info
Refer to the help topic "Fault avoidance" for further details.