Technical data

Glossary
System Software for S7-300/400 System and Standard Functions- Volume 2/2
A5E00739858-01
Glossary-13
Run-time Error
Errors which occur during execution of the user program in the PLC (not in the
process).
SCAN
An operating system function integrated in the CPU that is used to scan for and
detect a signal at set intervals in order to determine if a signal change has
occurred.
Standard Function
Standard functions are function blocks available from SIEMENS for implementing
complex tasks.
Standard Function Block
Standard function blocks are function blocks available from SIEMENS for
implementing complex tasks.
Start Event
Start events are defined events such as errors or interrupts which prompt the
operating system to call the appropriate organization block.
Start Event Information
The start event information is part of an organization block (OB). Start event
information provides the S7 user with detailed information about the event which
triggered the call for the OB. The start event information contains the event number
(consisting of event classes and event IDs), an event time stamp, and additional
information (for example, the address of the interrupt-activating signal module).
Start Information
When the operating system calls an organization block, the operating system
transfers start information which can be interpreted in the user program.
Startup OB
Depending on the setting of the startup mode selector (only S7-400), the reason for
the startup (return of power after outage, manual switch from STOP to RUN with
the mode selector or command from the programming device) either the startup
organization block "Complete restart" or "Restart" (only exists on the S7-400) is
called by the operating system. In the startup OB, the SIMATIC S7 user can, for
example, program how the system will start up again after a power outage.
An instruction (STEP 5 or STEP 7) is the smallest part of a program created in a
textual language. It represents a command for the processor.