Siemens S7-400 System Diagnostics, System Function SFC, System Function Block SFB, System Memory

Glossary

System Diagnostics

System diagnostics is the detection, evaluation, and reporting of errors occurring within the programmable controller. Examples of such errors are: program errors or failures on modules. System errors can be indicated with LED indicators or by STEP 7.

System Function (SFC)

An integral programmable function of the CPU operating system. Can be called in the user program. SFCs are not loaded as part of the program, because they are part of the operating system. SFCs do not have a memory function, same as FCs.

System Function Block (SFB)

An itegral function block of the CPU operating system. SFBs are not loaded as part of the program, because they are part of the operating system. Without memory function, same as SFCs. You need to create instance DBs for these blocks and load them into the CPU as part of the user program.

System Memory

The system memory is integrated in the CPU and executed in the form of RAM. The address areas (timers, counters, bit memory, etc.) and data areas required internally by the operating system (for example, backup for communication) are stored in the system memory.

T

Terminating resistor

Used to terminate data transfer lines in order to avoid reflections on the bus.

Time-Delay Interrupt

The time-delay interrupt belongs to one of the priority classes in SIMATIC S7-400 program processing. It is generated after expiry of a time started in the user program. A corresponding organization block is then executed.

Time-Of-Day Interrupt

The time-of-day interrupt belongs to a priotity class in SIMATIC S7-400 program program execution. It is generated depending on a certain date (or daily) and time of day (for example, 9:50 or hourly, per minute). A corresponding organization block is then executed.

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Automation System S7-400 Hardware and Installation A5E00850741-01