Siemens SIMATIC CP 340 User Manual page 192

Glossary
CPU
Central Processing Unit = Central module of the S7 Programmable Controller with control
and computing unit, memory, system program and interfaces to the I/O modules.
Cycle time
The cycle time is the time that the CPU requires to process the user program once.
Cyclic program processing
In cyclic program processing the user program runs in program loop, or cycle, that is
constantly repeated.
Data block (DB)
Data blocks are blocks that contain data and parameters with which the user program works.
Unlike all other blocks, they do not contain any instructions. There are global data blocks and
instance data blocks. The data contained in the data blocks can be accessed absolutely or
symbolically. Complex data can be stored in structured form.
Data Type
With the help of the data types you can specify how the value of a variable or constant in the
user program is to be used. The data types are divided into elementary and structured data
types
Default setting
The default setting is a reasonable basic setting that can be used whenever no other value is
specified.
Diagnostic buffer
Each CPU has its own diagnostic buffer, in which detailed information on all the diagnostic
events are entered in the sequence in which they occur.
The CP 340 has its own diagnostic buffer in which all diagnostic events of the CP 340 are
entered (hardware/firmware errors, initialization/parameterization errors, sending and
receiving errors).
Diagnostic events
Diagnostic events are such as module errors, system errors in the CPU which may be
caused by a program error or transitions from one operating mode to another.
192
PtP coupling and configuration of CP 340
Manual, 04/2011, A5E00369892-03