Siemens S7-400 Installation Manual page 306

Glossary
Reference Potential
The potential on which the voltages of the various circuits are based and according
to which they are measured.
Retentive Data
Retentive data are not lost after a power failure, if a backup battery is provided.
Revision Level
Products with the same order number are differentiated by their revision level. The
revision level is increased for upwardly-compatible function expansions, for
changes due to production reasons (use of new components) and for fault
correction.
Run-Time Error
Errors that occur in the programmable controller (that is, not in the process) during
execution of the user program.
S
Scan Cycle Time
The scan cycle time is the time the CPU takes to run the user program once
through.
Scan Rate
The scan rate defines how often GD packets are sent and received on the basis of
the CPU cycle.
SFB
³ System Function Block
SFC
³ System Function
Glossary-14
S7-400 and M7-400 Programmable Controllers Hardware and Installation
A5E00069481-04