Siemens Automation System S7-400 - Manual (Page 211)

Glossary
Glossary-3
Automation System S7-400 Hardware and Installation
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Counters
Counters are an area in the system memory of the CPU. The contents of these
counters can be changed using STEP 7 instructions (for example, up counter,
down counter).
CP
→ Communications Processor
CPU
Central processing unit of the S7 programmable controller with processor,
arithmetic unit, memory, operating system, and programming device interface.
Cycle time
The time a → CPU requires to execute the → user program.
Cyclic Interrupt
A cyclic interrupt is generated by the S7-400 CPU periodically according to a
programmable time interval. A corresponding organization block is then executed.
D
Data Block (DB)
Data blocks are areas in the user program which contain user data. There are
shared data blocks which can be accessed by all logic blocks, and there are
instance data blocks which are associated with a particular function block (FB) call.
Data, Static
Static data are data which are used only within a function block. These data are
stored in an instance data block belonging to the function block. The data stored in
the instance data block are retained until the next function block call.
Data, Temporary
Temporary data are local data of a block that are stored in the L stack during
processing of the block and that are not retained after processing.
Default Setting
A default setting is an expedient basic setting which is always used when no other
value is preset by a parameter.