Siemens SIMATIC PCS 7 Operating Manual page 85

4. F channel drivers for outputs
5. Placed automatically:
– F block F_PLK
– F block F_PSG_M
– F module driver for F-signal modules with outputs or with inputs and outputs
– F-communications blocks and F-system blocks for sending
– F block F_PLK_O
– F block F_DIAG (S7 F-Systems Lib V1_3 and higher)
The run sequence of the blocks listed under items 1 and 5 is adjusted automatically when
the F-program is compiled.
With F-Systems Lib V1_3 and higher, separate runtime groups are created for the F-blocks
listed under points 1 and 5 the first time compiling is performed.
The IPO principle (input, process, output) must always be observed when placing F-channel
drivers and F-blocks for user logic. This ensures that all inputs are read first, the relevant
processing steps are performed, and all outputs are then written.
Furthermore, F-runtime groups and F-monitoring blocks that are only visible following
compilation are also added automatically.
Note
No changes may be made in the automatically added runtime groups with the exception of
the scan cycle monitoring on "F_CYC_CO" blocks and the parameter assignment of the
"F_SHUTDN" block.
Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB
Configuring the safety program
7.2 Creating the safety program
85