A system function is a preprogrammed function that is integrated on the S7 CPU. You can call the SFC in your program. SFCs are part of the operating system and are not loaded as part of the program. Like FCs, SFCs are blocks "without memory."
S7 CPUs provide SFCs for the following functions:
• Copying and block functions
• Checking the program
• Handling the clock and run-time meters
• Transferring data sets
• Transferring events from a CPU to all other CPUs in multicomputing mode
• Handling time-of-day and time-delay interrupts
• Handling synchronous errors, interrupts, and asynchronous errors
• Information on static and dynamic system data, for example, diagnostics
• Process image updating and bit field processing
• Addressing modules
• Distributed I/O
• Global data communication
• Communication via non-configured connections
• Generating block-related messages
