Siemens SIMATIC S7 F Manual page 69

Safety Mechanisms
Note
Multiproject is a new feature of STEP7 V5.2, with this feature, you do not need to
maintain all CPUs in the same project; and you may have several projects in which
CPU to CPU communication is shared between them.
Communication with Standard CPUs
Direct communication between a Safety Program and a standard CPU is not
possible. Communication can only take place in a standard program on the F-CPU
after the F-data types have been converted into standard data types by means of a
conversion block. Communication in the standard program uses the standard
communication functions.
See Also
Programming Communication Between Safety Programs on Different CPUs
Fail-Safe Systems
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